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Search: id:A001154
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| A001154 |
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Describe the previous term! (method A - initial term is 9). |
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+0
11
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| 9, 19, 1119, 3119, 132119, 1113122119, 311311222119, 13211321322119, 1113122113121113222119, 31131122211311123113322119, 132113213221133112132123222119
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Method A = 'frequency' followed by 'digit'-indication.
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REFERENCES
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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.
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LINKS
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S. R. Finch, Conway's Constant
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EXAMPLE
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E.g. the term after 3119 is obtained by saying "one 3, two 1's, one 9", which gives 132119.
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MATHEMATICA
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RunLengthEncode[x_List] := (Through[{First, Length}[ #1]] &) /@ Split[x]; LookAndSay[n_, d_: 1] := NestList[Flatten[Reverse /@ RunLengthEncode[ # ]] &, {d}, n - 1]; F[n_] := LookAndSay[n, 9][[n]]; Table[FromDigits[F[n]], {n, 1, 11}] [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 08 2009]
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CROSSREFS
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Cf. A001155, A005150, A006751, A006715, A001140, A001141, A001143, A001145, A001151.
Sequence in context: A153316 A041160 A089565 this_sequence A138493 A022513 A156746
Adjacent sequences: A001151 A001152 A001153 this_sequence A001155 A001156 A001157
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KEYWORD
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nonn,base,easy,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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