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 A354138 #44 May 25 2022 09:08:29
%S A354138 1,1,13,389,4357,1960649,258805669,47102631757,11304631621681,
%T A354138 691843455246877,1314502564969066301,607300185015708631061,
%U A354138 335229702128671164345673,217899306383636256824687449,32946375125205802031892742289,848027998784883070051677094421
%N A354138 a(n) is the numerator of Sum_{k=0..n} (-1)^k / (2*k)!.
%F A354138 Numerators of coefficients in expansion of cos(sqrt(x)) / (1 - x).
%e A354138 1, 1/2, 13/24, 389/720, 4357/8064, 1960649/3628800, 258805669/479001600, ...
%t A354138 Table[Sum[(-1)^k/(2 k)!, {k, 0, n}], {n, 0, 15}] // Numerator
%t A354138 nmax = 15; CoefficientList[Series[Cos[Sqrt[x]]/(1 - x), {x, 0, nmax}], x] // Numerator
%o A354138 (PARI) a(n) = numerator(sum(k=0, n, (-1)^k/(2*k)!)); \\ _Michel Marcus_, May 24 2022
%Y A354138 Cf. A010050, A049470, A053557, A061354, A103816, A120265, A143382, A354211, A354332, A354334, A354378 (denominators).
%K A354138 nonn,frac
%O A354138 0,3
%A A354138 _Ilya Gutkovskiy_, May 24 2022