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 A012115 #12 Apr 12 2017 18:16:27
%S A012115 1,-1,1,-49,897,-96801,6803457,-1275363153,207592347393,
%T A012115 -60889593787713,17888210916886017,-7679611833095218545,
%U A012115 3530100224793651058305,-2109645360096014314212705,1387893136694794953345211905,-1109191050707015380265790041745,984063632341385922413073350925825
%N A012115 Expansion of e.g.f. of cos(arcsin(arcsinh(x))), even powers only.
%H A012115 G. C. Greubel, <a href="/A012115/b012115.txt">Table of n, a(n) for n = 0..224</a>
%e A012115 1 - 1/2!*x^2 + 1/4!*x^4 - 49/6!*x^6 + 897/8!*x^8...
%t A012115 With[{nn = 50}, Table[(CoefficientList[Series[Cos[ArcSin[ArcSinh[x]]], {x, 0, 2*nn}], x]*Range[0, 2*nn]!)[[n]], {n, 1, 2*nn + 1, 2}]] (* _G. C. Greubel_, Apr 12 2017 *)
%o A012115 (PARI) x = 'x + O('x^40); select(x->x, Vec(serlaplace(cos(asin(asinh(x)))))) \\ _Michel Marcus_, Mar 09 2017
%Y A012115 Cf. A012248.
%K A012115 sign
%O A012115 0,4
%A A012115 Patrick Demichel (patrick.demichel(AT)hp.com)
%E A012115 More terms from _Michel Marcus_, Mar 09 2017