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Search: id:A007651
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| A007651 |
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Describe the previous term! (method B - initial term is 1).
(Formerly M4768)
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+0
18
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| 1, 11, 12, 1121, 122111, 112213, 12221131, 1123123111, 12213111213113, 11221131132111311231, 12221231123121133112213111, 1123112131122131112112321222113113
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Method B = 'digit'-indication followed by 'frequency'.
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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).
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EXAMPLE
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E.g. the term after 1121 is obtained by saying "1 twice, 2 once, 1 once", which gives 122111.
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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, 1 ][ [ n ] ]; Table[ FromDigits[ Reverse[ F[ n ] ] ], {n, 1, 15} ]
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CROSSREFS
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Cf. A005150, A022470, A022499, A022500-A022505.
Sequence in context: A087304 A121808 A160265 this_sequence A022481 A156338 A034080
Adjacent sequences: A007648 A007649 A007650 this_sequence A007652 A007653 A007654
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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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