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Look-and-Say Sequence

Generate the look-and-say (Conway) sequence, step to the next or previous term, and find which term a number is.

The look-and-say sequence (also called Conway's sequence or the count-and-say sequence) builds each term by reading the digits of the term before it out loud, then writing down what you said. Starting from 1 you get 1, 11, 21, 1211, 111221, 312211, ...

Read 1211 as "one 1, one 2, two 1s", which you write as 111221. It turns up in puzzle caches as a "what comes next" sequence, so this tool can generate it from any seed, step a single term forward or backward, and tell you which term a given number is.

Generate the sequence

Digits only. The classic sequence starts at 1.

1 to 40. Terms grow quickly.

Step from a term

Next reads it aloud. Previous works only when the term is a valid look-and-say result.

Which term is it?