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 A290693 #7 Aug 09 2017 05:26:31 %S A290693 0,-1,1,0,-1,1,1,0,-3,2,0,1,0,-2,1,-2,0,5,0,-5,2,0,-3,0,5,0,-3,1,17,0, %T A290693 -42,0,35,0,-14,4,0,17,0,-28,0,14,0,-4,1,-62,0,153,0,-126,0,42,0,-9,2, %U A290693 0,-155,0,255,0,-126,0,30,0,-5,1 %N A290693 Triangle read by rows, coefficients of the polynomials P(n, x) = A135517(n) *(Euler(n, x) - Euler(n, 1)). %e A290693 0; %e A290693 -1, 1; %e A290693 0, -1, 1; %e A290693 1, 0, -3, 2; %e A290693 0, 1, 0, -2, 1; %e A290693 -2, 0, 5, 0, -5, 2; %p A290693 c := n -> `if`(n=1 or n mod 2 = 0, 1, 2*c(iquo(n, 2))): %p A290693 P := (n,x) -> (euler(n, x) - euler(n, 1))*c(n): %p A290693 seq(seq(coeff(P(n,x), x, k), k=0..n), n=0..9); %Y A290693 Cf. A135517. %K A290693 sign,tabl %O A290693 0,9 %A A290693 _Peter Luschny_, Aug 09 2017