Search: id:A001154
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%I A001154
%S A001154 9,19,1119,3119,132119,1113122119,311311222119,13211321322119,
%T A001154 1113122113121113222119,31131122211311123113322119,
%U A001154 132113213221133112132123222119
%N A001154 Describe the previous term! (method A - initial term is 9).
%C A001154 Method A = 'frequency' followed by 'digit'-indication.
%D A001154 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.
%D A001154 S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 452-455.
%D A001154 I. Vardi, Computational Recreations in Mathematica. Addison-Wesley, Redwood 
               City, CA, 1991, p. 4.
%H A001154 S. R. Finch, <a href="http://algo.inria.fr/bsolve/constant/cnwy/cnwy.html">
               Conway's Constant</a>
%e A001154 E.g. the term after 3119 is obtained by saying "one 3, two 1's, one 9", 
               which gives 132119.
%t A001154 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]
%Y A001154 Cf. A001155, A005150, A006751, A006715, A001140, A001141, A001143, A001145, 
               A001151.
%Y A001154 Sequence in context: A153316 A041160 A089565 this_sequence A138493 A022513 
               A156746
%Y A001154 Adjacent sequences: A001151 A001152 A001153 this_sequence A001155 A001156 
               A001157
%K A001154 nonn,base,easy,nice
%O A001154 1,1
%A A001154 N. J. A. Sloane (njas(AT)research.att.com).

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