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 A053485 #8 Jan 19 2017 02:33:45
%S A053485 1,1,1,3,1,15,45,21,315,2835,4725,22275,93555,2027025,42567525,
%T A053485 638512875,212837625,2170943775,13956067125,618718975875,
%U A053485 9280784638125,14992036723125,7522320180375,49308808782358125,147926426347074375
%N A053485 Denominators in expansion of exp(2x)/(1-x).
%H A053485 G. C. Greubel, <a href="/A053485/b053485.txt">Table of n, a(n) for n = 0..400</a>
%F A053485 a(n) = denominator( Sum_{k=0..n} 2^k/k! ). - _G. C. Greubel_, Jan 18 2017
%t A053485 Denominator[Table[Sum[2^k/k!, {k, 0, n}], {n, 0, 50}]] (* _G. C. Greubel_, Jan 18 2017 *)
%o A053485 (PARI) for(n=0,25, print1(denominator(sum(k=0,n, 2^k/k!)), ", ")) \\ _G. C. Greubel_, Jan 18 2017
%Y A053485 Cf. A053484, A010842.
%K A053485 nonn,frac
%O A053485 0,4
%A A053485 _N. J. A. Sloane_, Jan 15 2000