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 A308848 #11 Jul 03 2019 04:08:10
%S A308848 1,-1,-1,5,7,-71,-139,2071,5335,-103207,-331511,7853251,30256381,
%T A308848 -847377805,-3808492297,123081031165,632196102455,-23155450005175,
%U A308848 -133802756269735,5477371955388355,35167483918412257,-1591161899246627297,-11237664710770159597,556875003328690925825,4290500676272573740429
%N A308848 Expansion of e.g.f. exp(-x) / BesselI(0,2*x).
%C A308848 E.g.f. is inverse of e.g.f. for A002426 (central trinomial coefficients).
%F A308848 E.g.f.: 1 / Sum_{k>=0} A002426(k)*x^k/k!.
%t A308848 nmax = 24; CoefficientList[Series[Exp[-x]/BesselI[0, 2 x], {x, 0, nmax}], x] Range[0, nmax]!
%t A308848 a[0] = 1; a[n_] := a[n] = -Sum[Binomial[n, k] 3^k Hypergeometric2F1[1/2, -k, 1, 4/3] a[n - k], {k, 1, n}]; Table[a[n], {n, 0, 24}]
%o A308848 (PARI) my(x='x+O('x^30)); Vec(serlaplace(exp(-x) / besseli(0,2*x))) \\ _Michel Marcus_, Jul 02 2019
%Y A308848 Cf. A002426, A167022, A308847.
%K A308848 sign
%O A308848 0,4
%A A308848 _Ilya Gutkovskiy_, Jun 28 2019