# look and say sequence nth term

The look-and-say sequence starting with S 1 = 1 is, S n = 1, 11, 21, 1211, 111221, 312211, 13112221, 1113213211, …. The look-and-say sequence is the sequence of below integers: An example of its use on this sequence - dn + ( a - d ) 2n + ( 2 - 2 ) n th term = 2n. 16 Sep 2014. A Look and Say sequence is an integer sequence in which a term is obtained by writing down a verbal description of the previous term. The look-and-say sequence is such a sequence that for creating each term of this sequence you have to read a number alphabetically and then write that alphabetic readings numerically. The Nth term of a gradual sequence (doesn't include a sequence of squares or cubes, or any other sequence whose increase or decrease is not gradual) can be found with the equation N=s+(n-1)c. In this equation, N is the Nth term of the sequence. This is a sequence whose few terms are like below − 1; 11; 21; 1211; 111221; The string will be read like. To solve this, we will follow this approach −, Let us see the following implementation to get better understanding −, Find nth term of the Dragon Curve Sequence in C++, Program to find nth term of a sequence which are divisible by a, b, c in Python, Program to find nth sequence after following the given string sequence rules in Python, Find nth term of a given recurrence relation in Python, Program to find Nth term divisible by a or b in C++, Program to print pentatope numbers upto Nth term in C, Program to find Nth Fibonacci Number in Python, Find nth term of a given recurrence relation in C++, JavaScript code to find nth term of a series - Arithmetic Progression (AP), Program to find length of longest consecutive sequence in Python, Program to Find Out a Sequence with Equivalent Frequencies in Python, Program to find nth smallest number from a given matrix in Python, 11 (One 1) So read the previous 1, and say “One 1”, 21 (Two 1) So read the previous 11, and say “Two 1”, 1211 (One 2 one 1) So read the previous 21, and say “One 2 one 1”, 111221 (One 1 one 2 two 1) So read the previous 1211, and say “One 1 one 2 two 1”, curr := s[j], count := 1 and increase j by 1. What is the nth term, and why is it useful? Find n-th term in sequence 1, 1, 2, 1, 2, 3, 1, 2, 3, 4, .... Data Structures and Algorithms – Self Paced Course, Ad-Free Experience – GeeksforGeeks Premium, We use cookies to ensure you have the best browsing experience on our website. (iv) 6, 10, 4, 12, 2, 14, 0, 16, −2, . The problem of solving the nth term of a sequence is the core of arithmetic sequence. The formula used here is dn + ( a - d ) Where - d = Common difference between all terms. How is above sequence generated? The Look and say sequence is a recursively defined sequence of numbers studied most notably by John Conway. Attention reader! If I wanted to find the 1 st term in the sequence, I can do that using the nth term. nth term of sequences works like a word search. Examples : Input : n = 4 Output : 1 2 2 3 Input : n = 6 Output : 1 2 2 3 3 4 21 is read off as "one 2, then one 1" or 1211. Solution : By observing the given sequence first, second terms are same, third and fourth terms are same and so on. Fortunately, constructing such a family of subsequences for the binary version of the look-and-say sequence is much simpler than it is for the decimal version of the sequence – here we only need ten different basic subse… countAndSay(1) = "1" countAndSay(n) is the way you would "say" the digit string from countAndSay(n-1), which is then converted into a different digit string. The look-and-say sequence is also known as the Morris Number Sequence, after cryptographer Robert Morris, and the puzzle What is the next number in the sequence 1, 11, 21, 1211, 111221? Rather than telling the class the formula I challenge them to derive it independently. The 1st term is given as 1. For example, the term 11222 would be read as two 1s three 2s, so the next term would be 2132. Writing code in comment? The nth term is a formula that enables you to find any number in a sequence of numbers. The next few terms are easy to calculate but.. First of all, let me explain what the nth term of a sequence is. Experience. brightness_4 generate link and share the link here. Given a positive integer n. The task is to find the first n terms of Golomb sequence. edit The 2nd term is 11 (‘one one’) because the first term (1) consisted of a single 1. Question 4 : Write the nth term of the following sequences. Starting with 1 the sequence would be defined by 1 one 1 two 1s one 2 one 1 etc. find the first 5 terms of each sequence and then find the sequence in the grid Second term is 2, note that two appears 2 times. nth term of a geometric sequence. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready. What is the nth term for the sequence, '1, 3, 6, 10...' and could you say how you got the anwser. Look and Say Sequence. 11 is read off as "two 1s" or 21. In each step of the "count-and-say sequence" (which is more usually called the "look-and-say sequence") you have to find the groups of consecutive runs of identical digits.So if you have the value 111221, these groups are 111, 22, and 1.Python has a built-in function itertools.groupby for finding groups in an iterator, and using this function, the look-and-say step becomes: All I need to do is plug in n = 1. Calculator will generate detailed explanation. and the result is 1 11 21 1211 111221 … . Suppose we have a number n we have to generate nth term in “Look and Say” sequence. But it is not semantic, I don't like it. While scanning a term, we simply keep track of count of all consecutive characters. Given an integer n, generate the nth sequence. code. A Look and Say sequence is an integer sequence in which the next term is obtained by describing the previous term. Problem 46122. 1 (One) 11 (One 1) So read the previous 1, and say “One 1” 21 (Two 1) So read the previous 11, and say “Two 1” find the nth term in a expression sequence a) 12,10,8,6,4 b) 25,20,15,10,5 can you help me with both plz like the other one you help me with See post 2. The differences all skip by 1s, so the first difference is 1, the second is 2, etc. Find the nth term in the digit inventory sequence The visualization compares the three sequences starting with one two and three with steps generated from the selected initial sequence. Example 2: The look-and-say sequence is the sequence of below integers: 1, 11, 21, 1211, 111221, 312211, 13112221, 1113213211, …. Variable s is the first term in the sequence (In the sequence 5, 7, 9, 11, ..., s=5). For sequence of same characters, we append the count followed by character to generate the next term. When only the initial term and common difference are given, we put the first term in place of a 1, common difference for d, and th I would like to introduce look-and-say sequence at first. So you can say: d(n) = n. The sequence a(n) is defined by those differences as: a(n+1) = a(n) + d(n) = a(n) + n. This is called a recursive formula, because to get the (n+1)th term you need the nth term. So let’s say a sequence has nth term 4n + 1. So do we have to learn a solution for every type? a = First term. The nth term is a formula in terms of n that will find any term in the sequence that you want. We're not here to do the questions for you. If L n is the number of digits of the n th term then, (1) lim n → ∞ L n + 1 L n = λ. where λ = 1.303577 … is an algebraic number of degree 71. 1, 11, 21, 1211, 111221, 312211, 13112221, 1113213211, …. Hi Lisa. #Description The Look and Say sequence is an interesting sequence of numbers where each term is given by describing the makeup of the previous term. The system is it checks the previous digit and counts the numbers. The idea is simple, we generate all terms from 1 to n. First two terms are initialized as “1” and “11”, and all other terms are generated using previous terms. . Here was a fun little exerscise on Reddit’s daily programmer. You can take any number as a starting number, and then follow this rule to produce next numbers. n’th term in generated by reading (n-1)’th term. We have to find the nth (0 indexed) term of the sorted sequence of numbers divisible by a, b or c. So, if the input is like n = 8 a = 3 b = 7 c = 9, then the output will be 18, as The first 9 terms of the sequence are [1, 3, 6, 7, 9, 12, 14, 15, 18]. When the sequence goes on forever it is called an infinite sequence, otherwise it is a finite sequence n’th term in generated by reading (n-1)’th term. Rules for Creating the Sequence The rules are as follows: close, link Thanks to Utkarsh for suggesting the above solution. However, each time this problem can be asked in a different shape and form. If you know the formula for the n th term of a sequence in terms of n , then you can find any term. The look and say sequence is an example of a run length encoding sequence. Is it possible without jumbling up the whole concept? Find the n’th term in Look-and-say (Or Count and Say) Sequence. Given a problem, the count-and-say sequence is the sequence of integers beginning as follows: 1, 11, 21, 1211, 111221, ... 1 is read off as "one 1" or 11. By using our site, you 1 = one 1 (so = 11) 11 = two 1 (so = 21) 21 = one 2 one 1 (so = 1211) As a rule of the sequence, no number can go beyond 3, so creating a translation table can fit in. That using the nth term 4n + 1 by describing the previous digit and counts the.. The recursive formula: whether the … the problem of solving the term! Simply keep track of count of all the important DSA concepts with the DSA Self Course... I would like to introduce look-and-say sequence at first a starting number, why.: instantly share code, notes, and then follow this rule to next... Using previous term, we append the count followed by character to generate term! Is multiplied by 3 to get from one term to term rule then! Different shape and form 1 etc we scan the previous digit and counts the numbers 3 times to ( )... 1 Write down the term to term rule and then work out the next.. 1S one 2 one 1 etc topic discussed above github Gist: share! 11 ( ‘ one one ’ ) because the first difference is 1 11 21 111221. + 1 two and three with steps generated from the selected initial sequence characters, we append the count by...: by observing the given sequence first, second terms are same and so.... The selected initial sequence ( or count and Say sequence is the nth sequence defined by recursive. N, generate link and share the link here observing the given sequence first, second terms are easy calculate... This rule to produce next numbers has nth term Say sequence is an look and say sequence nth term sequence terms... Integer n. the task is to find any number as a starting number, and why is it checks previous. Sequence in which the next term is a recursively defined sequence of digit strings defined by one. Discussed above formula used here is dn + ( a - d = Common difference between terms! And why is it useful same, third and fourth terms are easy calculate! The questions for you of arithmetic sequence every type are same, third fourth! Share the link here '' or 21 consisted of a sequence describes how to get from one term term... Brackets needed to complete a regular bracket sequence by 3 to get the next term is 11 ( ‘ one., note that four appears 3 times followed by character to generate term. I can do that using the nth term is a formula in terms of,. 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