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A022507 Describe previous term from the right (method A - initial term is 3). 10
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

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

E.g. 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

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Last modified April 6 11:27 EDT 2020. Contains 333273 sequences. (Running on oeis4.)