A022507 - OEIS

A022507

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

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,1

COMMENTS

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

LINKS

Eric Weisstein's World of Mathematics, 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

CROSSREFS

KEYWORD

nonn,base,easy,nice

AUTHOR

EXTENSIONS

More terms from Erich Friedman

STATUS

approved