%I #16 Oct 15 2024 15:42:35
%S 1,1,1,2,2,2,3,4,4,4,4,4,5,5,6,7,7,7,7,7,7,7,7,7,8,8,8,9,10,10,11,12,
%T 12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,13,13,13,14,14,14,15,
%U 16,17,17,17,18,19,19,20,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21,21
%N Number of numbers <= n whose binary representation is without isolated ones.
%H Reinhard Zumkeller, <a href="/A173022/b173022.txt">Table of n, a(n) for n = 0..10000</a>
%F a(A144795(n+1)) = a(A144795(n)) + 1.
%F a(2^n - 1) = A005251(n+1).
%F A173021(n) <= a(n) <= A173023(n).
%e a(20) = #{0,3,6,7,12,14,15} = #{0,11,110,111,1100,1110,1111} = 7.
%t Accumulate[Array[Boole[FreeQ[Split[IntegerDigits[#, 2]], {1}]] &, 100, 0]] (* _Paolo Xausa_, Oct 15 2024 *)
%Y Cf. A005251, A007088, A144795, A173021, A173023.
%K base,nonn
%O 0,4
%A _Reinhard Zumkeller_, Feb 07 2010