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A006751 Describe the previous term! (method A - initial term is 2).
(Formerly M2052)
+0
23
2, 12, 1112, 3112, 132112, 1113122112, 311311222112, 13211321322112, 1113122113121113222112, 31131122211311123113322112, 132113213221133112132123222112 (list; graph; listen)
OFFSET

1,1

COMMENT

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

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

J. H. Conway, The weird and wonderful chemistry of audioactive decay, in T. M. Cover and Gopinath, eds., Open Problems in Communication and Computation, Springer, NY 1987, pp. 173-188.

S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 452-455.

I. Vardi, Computational Recreations in Mathematica. Addison-Wesley, Redwood City, CA, 1991, p. 4.

LINKS

S. R. Finch, Conway's Constant

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

EXAMPLE

E.g. the term after 3112 is obtained by saying "one 3, two 1's, one 2", which gives 132112.

MATHEMATICA

RunLengthEncode[ x_List ] := (Through[ {First, Length}[ #1 ] ] &) /@ Split[ x ]; LookAndSay[ n_, d_:1 ] := NestList[ Flatten[ Reverse /@ RunLengthEncode[ # ] ] &, {d}, n - 1 ]; F[ n_ ] := LookAndSay[ n, 2 ][ [ n ] ]; Table[ FromDigits[ F[ n ] ], {n, 1, 11} ] - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 21 2007

CROSSREFS

Cf. A001155, A005150, A006715, A001140, A001141, A001143, A001145, A001151, A001154.

Adjacent sequences: A006748 A006749 A006750 this_sequence A006752 A006753 A006754

Sequence in context: A058975 A057120 A112512 this_sequence A023989 A001389 A022914

KEYWORD

nonn,base,easy,nice

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com).

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Last modified November 8 07:45 EST 2009. Contains 166143 sequences.


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