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 A088990 #5 Feb 22 2013 14:38:49 %S A088990 1,0,1,0,1,1,0,1,8,1,0,1,51,51,1,0,1,310,1194,310,1,0,1,1865,21790, %T A088990 21790,1865,1,0,1,11196,357975,975656,357975,11196,1,0,1,67183, %U A088990 5603421,35471987,35471987,5603421,67183,1 %N A088990 Triangle related to generalized Euler numbers of type 2^n (A005799). %C A088990 T(n+1,n) = T(n+1,2) = Sum(0<=k<=n, (n-k)*6^k ). %F A088990 Triangle T(n, k), read by rows, given by [0, 1, 0, 6, 0, 15, 0, 28, 0, 45, 0, 66, 0, ...] DELTA [1, 0, 6, 0, 15, 0, 28, 0, 45, 0, 66, 0, ...] where DELTA is the operator defined in A084938. %Y A088990 Cf. A005799 (row sums), A084938. %K A088990 easy,nonn,tabl %O A088990 0,9 %A A088990 _Philippe Deléham_, Nov 01 2003