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 A080896 #14 Feb 28 2017 22:33:59
%S A080896 1,1,3,25,265,3741,64051,1298053,30295665,800411545,23601417571,
%T A080896 768200763441,27352316065273,1057402991121205,44102326806885075,
%U A080896 1973793512480683741,94345589402816289121,4796647490592139950513
%N A080896 Expansion of the exponential series exp( x * T(x) ) = exp( x / sqrt(1 - 2*x - 3*x^2) ), where T(x) is the ordinary generating series of the central trinomial coefficients (A002426).
%H A080896 G. C. Greubel, <a href="/A080896/b080896.txt">Table of n, a(n) for n = 0..379</a> (terms 0..100 from T. D. Noe)
%F A080896 E.g.f.: exp(x/sqrt(1 - 2*x - 3*x^2)).
%t A080896 With[{nn=20},CoefficientList[Series[Exp[x/Sqrt[1-2 x-3x^2]],{x,0,nn}], x]Range[0,nn]!] (* _Harvey P. Dale_, Sep 08 2011 *)
%o A080896 (PARI) x='x + O('x^50); Vec(serlaplace(exp(x/sqrt(1 - 2*x - 3*x^2)))) \\ _G. C. Greubel_, Feb 27 2017
%Y A080896 Cf. A002426.
%K A080896 easy,nice,nonn
%O A080896 0,3
%A A080896 _Emanuele Munarini_, Mar 31 2003