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%I A079071 #15 Apr 18 2018 18:22:42
%S A079071 0,0,0,0,0,0,1,0,0,0,1,0,2,1,2,0,0,0,1,0,2,1,2,0,3,3,4,1,5,2,3,0,0,0,
%T A079071 1,0,2,1,2,0,3,3,4,1,5,2,3,0,4,6,7,4,8,5,6,1,9,7,8,2,9,3,4,0,0,0,1,0,
%U A079071 2,1,2,0,3,3,4,1,5,2,3,0,4,6,7,4,8,5,6,1,9,7,8,2,9,3,4,0,5,10,11,10,12,11,12
%N A079071 Number of numbers < n whose binary representation has the same number of 0's and 1's as n does.
%H A079071 Alois P. Heinz, <a href="/A079071/b079071.txt">Table of n, a(n) for n = 0..16383</a>
%p A079071 f:= n-> (x-> (t-> t*(t+1)/2+x[2])(x[1]+x[2]))(add(
%p A079071     `if`(i=0, [1, 0], [0, 1]), i=convert(n, base, 2))):
%p A079071 b:= proc(n) b(n):= b(n-1)+x^f(n) end: b(-1):=0:
%p A079071 a:= n-> coeff(b(n-1), x, f(n)):
%p A079071 seq(a(n), n=0..150);  # _Alois P. Heinz_, Feb 08 2018
%t A079071 a[n_] := Count[Range[n-1], k_ /; DigitCount[n, 2] == DigitCount[k, 2]];
%t A079071 Table[a[n], {n, 0, 104}] (* _Jean-François Alcover_, Feb 13 2018 *)
%Y A079071 Cf. A079070, A068076, A079074, A007088, A023416, A000120.
%K A079071 nonn,look
%O A079071 0,13
%A A079071 _Reinhard Zumkeller_, Dec 21 2002

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