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 A336171 #13 Jul 10 2020 22:10:05 %S A336171 1,119,112681,166923119,302857024681,616967236620839, %T A336171 1354737230950753441,3135180238488702264959,7543003841027749147438441, %U A336171 18698821633118804601271092959,47466852090165503045193665276041,122841260732098480578334554450553679,323029586700918689286922557725358306721 %N A336171 a(n) = Sum_{k=0..n} (-1)^(n-k) * (n+4*k)!/((n-k)! * k!^5). %C A336171 Diagonal of the rational function 1 / (1 - Sum_{k=1..5} x_k + Product_{k=1..5} x_k). %F A336171 G.f.: Sum_{k>=0} (5*k)!/k!^5 * x^k / (1+x)^(5*k+1). %t A336171 a[n_] := Sum[(-1)^(n - k)*(n + 4*k)!/((n - k)!*k!^5), {k, 0, n}]; Array[a, 13, 0] (* _Amiram Eldar_, Jul 10 2020 *) %o A336171 (PARI) {a(n) = sum(k=0, n, (-1)^(n-k)*(n+4*k)!/((n-k)!*k!^5))} %o A336171 (PARI) N=20; x='x+O('x^N); Vec(sum(k=0, N, (5*k)!/k!^5*x^k/(1+x)^(5*k+1))) %Y A336171 Column k=5 of A336169. %Y A336171 Cf. A082489. %K A336171 nonn %O A336171 0,2 %A A336171 _Seiichi Manyama_, Jul 10 2020