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Search: id:A045918
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| A045918 |
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Describe n. Also called the "Say What You See" or "Look and Say" sequence LS(n). |
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+0
13
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| 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 1110, 21, 1112, 1113, 1114, 1115, 1116, 1117, 1118, 1119, 1210, 1211, 22, 1213, 1214, 1215, 1216, 1217, 1218, 1219, 1310, 1311, 1312, 23, 1314, 1315, 1316, 1317, 1318, 1319, 1410, 1411, 1412
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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a(111111111)=a((10^10-1)/9)=101 is the first term with an odd number of digits; 3-digit terms are unambiguous, but already the 2nd 4-digit term is LS( 12 ) = 1112 = LS( 2*(10^111-1)/9 ) ("hundred eleven 2's"). The smallest n such that LS(n)=LS(k) for some k<n (i.e. the largest n such that the restriction of LS to [0..n-1] is injective) appears to be 10*(10^11-1)/9 : LS(eleven '1's, one '0') = 11110 = LS(one '1', eleven '0's). - M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Nov 14 2006
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EXAMPLE
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23 has "one 2, one 3", so a(23) = 1213.
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MAPLE
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LS:=n-> if n>9 then LS(op(convert(n, base, 10))) else for i from 2 to nargs do if args[i] <> n then RETURN(( LS( args[i..nargs] )*10^length(i-1) + i-1)*10 + n ) fi od: 10*nargs + n fi; - M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Nov 14 2006
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CROSSREFS
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Cf. A005150.
Sequence in context: A047842 A047843 A097598 this_sequence A088476 A008715 A115844
Adjacent sequences: A045915 A045916 A045917 this_sequence A045919 A045920 A045921
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KEYWORD
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nonn,base
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AUTHOR
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njas
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