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%I #25 Feb 17 2021 01:57:31
%S 0,1,2,3,4,5,7,8,9,10,11,14,15,16,17,18,19,20,21,22,23,28,29,30,31,32,
%T 33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,56,57,58,59,60,61,62,63,
%U 64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86
%N Numbers whose binary expansion does not begin 110.
%F a(n) = n - 1, 1 <= n <= 6, a(2^(m+2) + 2^m + k + 2) = 2^(m+2) + 2^(m+1) + 2^m + k, m >= 0, 0 <= k < (2^(m+2) + 2^m). - _Yosu Yurramendi_, Aug 08 2016
%t Flatten[Insert[Select[Range[120], If[Length[IntegerDigits[ #, 2]] >= 3, Not[IntegerDigits[ #, 2][[1]] == 1 && IntegerDigits[ #, 2][[2]] == 1 && IntegerDigits[ #, 2][[3]] == 0 ]] &], {0, 1, 2, 3}, 1]] (* _Stefan Steinerberger_, Apr 15 2006 *)
%t Join[{0,1,2,3},Select[Range[4,90],Take[IntegerDigits[#,2],3]!={1,1,0}&]] (* _Harvey P. Dale_, Feb 27 2012 *)
%Y Cf. A007088.
%K nonn,easy,base
%O 1,3
%A _N. J. A. Sloane_
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