A022507 Describe previous term from the right (method A - initial term is 3).

3, 13, 1311, 211311, 21132112, 122112132112, 122112131112212211, 2122112231131112212211, 21221122311321132221221112, 12312211321321121321132221221112

Offset

0,1

Comments

Method A = 'frequency' followed by 'digit'-indication.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 0..21

Eric Weisstein's World of Mathematics, Look and Say Sequence

Wikipedia, Look-and-say sequence

Formula

a(n+1) = A045918(A004086(a(n))). - Reinhard Zumkeller, Mar 02 2014

Example

The term after 1311 is obtained by saying "two 1's, one 3, one 1", which gives 211311.

Mathematica

A022507[1]:=3; A022507[n_]:=A022507[n]=FromDigits[Flatten[{Length[#], First[#]}&/@Split[Reverse[IntegerDigits[A022507[n-1]]]]]]; Map[A022507, Range[15]] (* Peter J. C. Moses, Apr 22 2013 *)

Prog

(Haskell)
a022507 n = a022507_list !! n
a022507_list = iterate (a045918 . a004086) 3
-- Reinhard Zumkeller, Mar 02 2014

Crossrefs

Cf. A022506, A006711, A022482, A022508-A022513.

Sequence in context: A006715 A177362 A138487 * A108583 A127855 A087333

Adjacent sequences: A022504 A022505 A022506 * A022508 A022509 A022510

Keyword

nonn,base,easy,nice

Author

N. J. A. Sloane

Extensions

More terms from Erich Friedman

Status

approved