%I A007651 M4768
%S A007651 1,11,12,1121,122111,112213,12221131,1123123111,12213111213113,
%T A007651 11221131132111311231,12221231123121133112213111,
%U A007651 1123112131122131112112321222113113
%N A007651 Describe the previous term! (method B - initial term is 1).
%C A007651 Method B = 'digit'-indication followed by 'frequency'.
%D A007651 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%e A007651 E.g. the term after 1121 is obtained by saying "1 twice, 2 once, 1 once", 
               which gives 122111.
%t A007651 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} 
               ]
%Y A007651 Cf. A005150, A022470, A022499, A022500-A022505.
%Y A007651 Sequence in context: A087304 A121808 A160265 this_sequence A022481 A156338 
               A034080
%Y A007651 Adjacent sequences: A007648 A007649 A007650 this_sequence A007652 A007653 
               A007654
%K A007651 nonn,base,easy,nice
%O A007651 1,2
%A A007651 N. J. A. Sloane (njas(AT)research.att.com).