Search: id:A045918
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%I A045918
%S A045918 10,11,12,13,14,15,16,17,18,19,1110,21,1112,1113,1114,1115,1116,
%T A045918 1117,1118,1119,1210,1211,22,1213,1214,1215,1216,1217,1218,1219,
%U A045918 1310,1311,1312,23,1314,1315,1316,1317,1318,1319,1410,1411,1412
%N A045918 Describe n. Also called the "Say What You See" or "Look and Say" sequence 
               LS(n).
%C A045918 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
%e A045918 23 has "one 2, one 3", so a(23) = 1213.
%p A045918 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
%Y A045918 Cf. A005150.
%Y A045918 Sequence in context: A047842 A047843 A097598 this_sequence A088476 A008715 
               A115844
%Y A045918 Adjacent sequences: A045915 A045916 A045917 this_sequence A045919 A045920 
               A045921
%K A045918 nonn,base
%O A045918 0,1
%A A045918 N. J. A. Sloane (njas(AT)research.att.com).

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