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 A014780 #22 Jun 03 2022 03:24:57 %S A014780 1,1,1,1,3,3,5,3,3,17,17,31,25,31,17,17,155,155,293,259,349,259,293, %T A014780 155,155,2073,2073,3991,3681,5151,4289,5151,3681,3991,2073,2073,38227, %U A014780 38227,74381,70235,100325,88507,109765,88507,100325,70235,74381,38227 %N A014780 Triangle of numbers associated with Genocchi numbers. %C A014780 When written in the triangle form as in the example below, the k-th entry (k>=1) in row n (n>=1) is the number of Dumont permutations of the first kind of length 2*n that start with k+1. - _Alexander Burstein_, May 14 2022 %H A014780 G. Kreweras, <a href="https://doi.org/10.1006/eujc.1995.0081">Sur les permutations comptées par les nombres de Genocchi de 1-ière et 2-ième espèce</a>, Europ. J. Comb., vol. 18, pp. 49-58, 1997. %F A014780 Row sums give A110501. %e A014780 Triangle begins: %e A014780 1; %e A014780 1, 1, 1; %e A014780 3, 3, 5, 3, 3; %e A014780 17, 17, 31, 25, 31, 17, 17; %e A014780 ... %Y A014780 Cf. A110501, A014782, A014783, A014784. %K A014780 tabf,nonn,easy %O A014780 1,5 %A A014780 _N. J. A. Sloane_ %E A014780 More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 22 2003