%I A119972
%S A119972 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,
               27,
%T A119972 28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,
               51,
%U A119972 52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,
               75
%V A119972 1,2,-3,4,5,-6,-7,8,9,10,-11,-12,13,-14,-15,16,17,18,-19,20,21,-22,-23,
               -24,25,26,-27,
%W A119972 -28,29,-30,-31,32,33,34,-35,36,37,-38,-39,40,41,42,-43,-44,45,-46,-47,
               -48,49,50,-51,
%X A119972 52,53,-54,-55,-56,57,58,-59,-60,61,-62,-63,64,65,66,-67,68,69,-70,-71,
               72,73,74,-75
%N A119972 Flag n when the first difference of the decimal encoding of the Gray 
               code is negative.
%F A119972 Merge A091072 with minus A091067 maintaining increasing absolute value.
%e A119972 A003188 begins 0 1 3 2 6 7 5 4 12 13 15 14 10 11 9 8 24 ...so
%e A119972 A055975 begins 1 2-1 4 1-2-1 8 1 2 -1 -4 1 -2-1 16 ...
%e A119972 so the negative positions are located at 3,6,7,11,12,14,..., = A091067
%e A119972 and the positive positions at the complement of A091067 which is A091072.
%p A119972 isA091067 := proc(n) option remember ; if n mod 4 = 3 then RETURN(true) 
               ; else if n mod 2 = 0 then if isA091067(n/2) then RETURN(true) ; 
               fi ; fi ; RETURN(false) ; fi ; end: A119972 := proc(n) if isA091067(n) 
               then -n ; else n ; fi ; end: for n from 1 to 180 do printf("%d, ",
               A119972(n)) ; od ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               May 14 2007
%Y A119972 Cf. A003188, A055975, A091067, A091072.
%Y A119972 Sequence in context: A023443 A099570 A020725 this_sequence A131738 A000027 
               A001477
%Y A119972 Adjacent sequences: A119969 A119970 A119971 this_sequence A119973 A119974 
               A119975
%K A119972 easy,sign
%O A119972 1,2
%A A119972 Alford Arnold (Alford1940(AT)aol.com), Jun 01 2006
%E A119972 More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 14 2007