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 A356668 #15 Aug 22 2022 10:06:03 %S A356668 1,1,3,7,37,121,1141,5041,60761,378001,5444461,39916801,729041545, %T A356668 6227020801,130767460825,1321314894901,31388220966961,355687428096001, %U A356668 9636906872926477,121645100408832001,3649432697160095561,51223991519836175041,1686001091666419279753 %N A356668 Expansion of e.g.f. Sum_{k>=0} x^k / (k! - k*x^k). %F A356668 Expansion of e.g.f. Sum_{k>=0} x^k / (k! * (1 - k*x^k/k!)). %F A356668 a(n) = n! * Sum_{d|n} 1/(d * (d-1)!^(n/d)) for n > 0. %F A356668 a(p) = 1 + p! for prime p. %t A356668 a[n_]:= n! * DivisorSum[n, 1/(# * (# - 1)!^(n/#)) &]; a[0] = 1; Array[a, 23, 0] (* _Amiram Eldar_, Aug 22 2022 *) %o A356668 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(sum(k=0, N, x^k/(k!-k*x^k)))) %o A356668 (PARI) a(n) = if(n==0, 1, n!*sumdiv(n, d, 1/(d*(d-1)!^(n/d)))); %Y A356668 Cf. A356029, A356328, A356608. %Y A356668 Cf. A038507, A327578, A356667. %K A356668 nonn %O A356668 0,3 %A A356668 _Seiichi Manyama_, Aug 22 2022