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 A256402 #12 Mar 30 2015 09:41:57
%S A256402 1,1,1,3,3,5,45,63,105,405,14175,17325,18711,552825,14189175,49116375,
%T A256402 91216125,144729585,97692469875,109185701625,1031198293125,
%U A256402 10257709336875,3430178002251,2348038513445625,1034450533895625,160789593855515625,16025362854266390625
%N A256402 Denominators of coefficients of expansion of exp(-Sum_{k=0..oo} x^(2^k)/2^k ) in powers of x.
%H A256402 Hiroaki Yamanouchi, <a href="/A256402/b256402.txt">Table of n, a(n) for n = 0..100</a>
%H A256402 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 A256402 For numerators see A256401. Cf. A256400.
%K A256402 nonn,frac
%O A256402 0,4
%A A256402 _N. J. A. Sloane_, Mar 29 2015
%E A256402 a(18)-a(26) from _Hiroaki Yamanouchi_, Mar 30 2015