This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A094812 #11 Sep 24 2018 16:53:14
%S A094812 0,0,0,2,3,9,19,41,85,181,375,769,1584,3224,6580,13354,27059,54521,
%T A094812 110682,223509,450702,908240,1828936,3680596,7402790,14883096,
%U A094812 29908688,60081574,120655821,242228178,486173375,975559168,1957148063,3925643991
%N A094812 Number of odd composites between 2^n and 2^(n + 1).
%C A094812 This sequence may be related to n-ary rooted trees of a fixed height. For instance, the first few terms of A036616 are:
%C A094812 1, 1, 1, 2, 4, 9, 19, 41, 86, 182, 376, 776, 1579, ...
%C A094812 and in A036622:
%C A094812 1, 1, 1, 2, 4, 9, 19, 42, 88, 188, 393, 821, 1692, ...
%C A094812 whereas in the present sequence we have:
%C A094812 0, 0, 0, 2, 3, 9, 19, 41, 85, 181, 375, 769, 1584, ...
%F A094812 Members of A071904 that lie between 2^n and 2^(n + 1).
%e A094812 a(3) = 2 because in the interval 2^3..2^4 = [8..16] there are two odd composites: 9 = 3^2, 15 = 3 * 5.
%t A094812 f[n_] := (2^(n - 1) - PrimePi[2^(n + 1)] + PrimePi[2^n]); Table[ f[n], {n, 32}] (* _Robert G. Wilson v_, Jun 15 2004 *)
%Y A094812 Cf. A036616, A036622, A071904.
%K A094812 easy,nonn
%O A094812 0,4
%A A094812 _Andrew S. Plewe_, Jun 11 2004
%E A094812 More terms from _Robert G. Wilson v_, Jun 15 2004