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A023989 Look and Say sequence: describe the previous term! (method C - initial term is 2). 6
2, 12, 1112, 3112, 211213, 312213, 212223, 114213, 31121314, 41122314, 31221324, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Method C = 'frequency' followed by 'digit'-indication with digits in increasing order.

Converges to 21322314 at the eleventh term. Depending on the initial value, the sequence may converge to a cycle of 2 or more values, for example : 123456, 111213141516, 711213141516, 611213141516, 611213141526, 512213141526, 413213142516, 412223241516, 314213241516, 412223241516, 314213241516, 412223241516

a(n) = A005151(n) for n > 6. - Reinhard Zumkeller, Jan 26 2014

LINKS

Table of n, a(n) for n=0..26.

EXAMPLE

a(1) = 12, so a(2) = 1112 because 12 contains a digit 1 and a digit 2; a(3) = 3112 because 1112 contains three digits 1 and a digit 2

PROG

(Haskell)

import Data.List (group, sort, transpose)

a023989 n = a023989_list !! (n-1)

a023989_list = 2 : f [2] :: [Integer] where

   f xs = (read $ concatMap show ys) : f (ys) where

          ys = concat $ transpose [map length zss, map head zss]

          zss = group $ sort xs

-- Reinhard Zumkeller, Jan 26 2014

CROSSREFS

Cf. A005150, A022481.

Cf. A045918, A118628.

Sequence in context: A057120 A112512 A006751 * A001389 A022914 A177361

Adjacent sequences:  A023986 A023987 A023988 * A023990 A023991 A023992

KEYWORD

nonn,base

AUTHOR

Artemario Tadeu Medeiros da Silva (artemario(AT)uol.com.br), Mar 19 2002

STATUS

approved

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Last modified December 3 04:39 EST 2016. Contains 278698 sequences.