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 A336242 #6 Jul 13 2020 22:21:05
%S A336242 1,3,37,431,14401,403199,25401601,1216454399,135339724801,
%T A336242 9877056537599,1593350922240001,178056522962841599,
%U A336242 38775788043632640001,5700041141609893478399,1757631343928533032960001,327562346808114783805439999,126513546505547170185216000001
%N A336242 a(n) = (n!)^2 * Sum_{d|n} (-1)^(d+1) / (d!)^2.
%F A336242 a(n) = (n!)^2 * [x^n] Sum_{k>=1} (1 - BesselJ(0,2*x^(k/2))).
%F A336242 a(n) = (n!)^2 * [x^n] Sum_{k>=1} -(-x)^k / ((k!)^2 * (1 - x^k)).
%t A336242 Table[(n!)^2 Sum[(-1)^(d + 1)/(d!)^2, {d, Divisors[n]}], {n, 1, 17}]
%t A336242 nmax = 17; CoefficientList[Series[Sum[(1 - BesselJ[0, 2 x^(k/2)]), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!^2 // Rest
%o A336242 (PARI) a(n) = n!^2*sumdiv(n, d, (-1)^(d+1)/d!^2); \\ _Michel Marcus_, Jul 13 2020
%Y A336242 Cf. A073701, A132958, A336241.
%K A336242 nonn
%O A336242 1,2
%A A336242 _Ilya Gutkovskiy_, Jul 13 2020