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Search: id:A005151
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| A005151 |
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Summarize the previous term! (in increasing order).
(Formerly M4779)
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+0
30
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| 1, 11, 21, 1112, 3112, 211213, 312213, 212223, 114213, 31121314, 41122314, 31221324, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314, 21322314
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
V. Bronstein and A. S. Fraenkel, On a curious property of counting sequences, Amer. Math. Monthly, 101 (1994), 560-563.
Problem in J. Recreational Math., 30 (4) (1999-2000), p. 309.
C. Fleenor, "A litteral sequence", Solution to Problem 2562, Journal of Recreational Mathematics, vol. 31 No. 4 pp. 307 2002-3 Baywood NY.
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LINKS
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Madras Math's Amazing Number Facts, Fact No. 13
Madras Math, Descriptive Number
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EXAMPLE
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For example, the term after 312213 is obtained by saying "Two 1's, two 2's, two 3's", which gives 21-22-23, i.e. 212223.
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MATHEMATICA
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RunLengthEncode[x_List] := (Through[{Length, First}[ #1]] &) /@ Split[ Sort[x]]; LookAndSay[n_, d_:1] := NestList[ Flatten[ RunLengthEncode[ # ]] &, {d}, n - 1]; F[n_] := LookAndSay[n, 1][[n]]; Table[ FromDigits[ F[n]], {n, 25}] (from Robert G. Wilson v Jan 22 2004).
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CROSSREFS
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Cf. A005150. See A083671 for another version.
Cf. A047842.
Sequence in context: A092806 A138485 A006711 this_sequence A098155 A098154 A158081
Adjacent sequences: A005148 A005149 A005150 this_sequence A005152 A005153 A005154
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KEYWORD
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nonn,base,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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