A022482 Describe previous term from the right (method A - initial term is 2).

2, 12, 1211, 211211, 21122112, 1221222112, 122132112211, 2122211213112211, 21222113111221321112, 123112131122311321321112, 123112131112132113222113111221131211

Offset

1,1

Comments

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

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..22

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

E.g. the term after 1211 is obtained by saying "two 1's, one 2, one 1", which gives 211211.

Mathematica

A022482[1]:=2; A022482[n_]:=A022482[n]=FromDigits[Flatten[{Length[#], First[#]}&/@Split[Reverse[IntegerDigits[A022482[n-1]]]]]]; Map[A022482, Range[15]] (* Peter J. C. Moses, Apr 22 2013 *)

Prog

(Haskell)
a022482 n = a022482_list !! (n-1)
a022482_list = iterate (a045918 . a004086) 2
-- Reinhard Zumkeller, Mar 02 2014

Crossrefs

Cf. A022506, A006711, A022507-A022513.

Sequence in context: A022914 A177361 A138486 * A372198 A081701 A069714

Adjacent sequences: A022479 A022480 A022481 * A022483 A022484 A022485

Keyword

nonn,base,easy,nice

Author

Clark Kimberling

Status

approved