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

Author

N. J. A. Sloane

Keywords

• nonn
• base
• easy
• nice

Comments

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

Examples

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

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

Crossrefs

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

Programs

Haskell

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

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 *)

Formula

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

Extensions

More terms from Erich Friedman