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 A168562 #8 Sep 14 2020 17:03:22 %S A168562 1,1,2,18,244,5710,188908,8702820,524888040,40393084950,3853034107900, %T A168562 446671026849916,61824801560228056,10072685383683311116, %U A168562 1907978676359896992824,415795605119514578204616,103294156408291202467520976,29018125910193347265466916070 %N A168562 Sum of squares of Eulerian numbers in row n of triangle A008292 with a(0)=1. %C A168562 Row sums of Eulerian triangle A008292 yield the factorials. %H A168562 Alois P. Heinz, <a href="/A168562/b168562.txt">Table of n, a(n) for n = 0..253</a> %F A168562 a(n) = Sum_{k=0..n} [ Sum_{j=0..k} (-1)^j*(k-j)^n*C(n+1, j) ]^2. %e A168562 a(1) = 1 = 1; %e A168562 a(2) = 1 + 1 = 2; %e A168562 a(3) = 1 + 4^2 + 1 = 18; %e A168562 a(4) = 1 + 11^2 + 11^2 + 1 = 244; %e A168562 a(5) = 1 + 26^2 + 66^2 + 26^2 + 1 = 5710; %e A168562 a(6) = 1 + 57^2 + 302^2 + 302^2 + 57^2 + 1 = 188908. %p A168562 a:= n-> add(combinat[eulerian1](n, k)^2, k=0..n): %p A168562 seq(a(n), n=0..18); # _Alois P. Heinz_, Sep 10 2020 %o A168562 (PARI) {a(n)=sum(k=0,n,sum(j=0, k, (-1)^j*(k-j)^n*binomial(n+1, j))^2)} %Y A168562 Cf. A008292. %Y A168562 Column k=2 of A335545. %K A168562 nonn %O A168562 0,3 %A A168562 _Paul D. Hanna_, Nov 29 2009