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 A256400 #13 Mar 30 2015 09:42:22
%S A256400 1,1,1,2,2,7,16,67,88,617,2626,18176,6949,423271,2172172,19151162,
%T A256400 58438907,899510224,7656246634,1236339998,460251204914,6682341795214,
%U A256400 55431849118769,58399157390146,2845938531282919,54648005951674444,12207653488921678
%N A256400 Numerators of coefficients of expansion of exp( Sum_{k=0..oo} x^(2^k)/2^k ) in powers of x.
%H A256400 Hiroaki Yamanouchi, <a href="/A256400/b256400.txt">Table of n, a(n) for n = 0..100</a>
%H A256400 Koda, Tatsuhiko; Sato, Masaki; Takegahara, Yugen; <a href="http://dx.doi.org/10.1142/S0219498815500528">2-adic properties for the numbers of involutions in the alternating groups</a>, J. Algebra Appl. 14 (2015), no. 4, 1550052 (21 pages). See Lemma 2.1.
%Y A256400 For denominators see A049606. Cf. A256401/A256402.
%K A256400 nonn,frac
%O A256400 0,4
%A A256400 _N. J. A. Sloane_, Mar 29 2015
%E A256400 a(18)-a(26) from _Hiroaki Yamanouchi_, Mar 30 2015