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 A129398 #4 Jul 11 2015 16:50:04 %S A129398 1,1,1,5,1,1,1,1,-3,1,1,-3,-7,-3,1,1,-3,1,1,1,1,4,1,1,3,0,3,1,1,4,0, %T A129398 -7,0,4,1,1,3,0,3,1,1,4,1,1 %N A129398 Pyramid P(h,x,y)=P(h,x,y-1)+P(h,x,y+1)+P(h,x-1,y)+P(h,x+1,y)+P(h-1,x,y), read level by level, x by x. %C A129398 All face elements=1. For an element x on a level inside the pyramid %C A129398 ..b %C A129398 .cxd %C A129398 ..e %C A129398 with a above x, x=a+b+c+d+e. Every level of the pyramid is symmetric. Thus the top (h=0) of the pyramid is 1. The level h=1 is %C A129398 ..1 %C A129398 .1.5.1 %C A129398 ..1 %C A129398 The level h=2 is %C A129398 .....1 %C A129398 ..1.-3..1 %C A129398 1.-3.-7.-3..1 %C A129398 ..1.-3..1 %C A129398 .....1 %C A129398 The level h=3 is %C A129398 ........1 %C A129398 .....1..4..1 %C A129398 ..1..3..0..3..1 %C A129398 1..4..0.-7..0..4..1 %C A129398 ..1..3..0..3..1 %C A129398 .....1..4..1 %C A129398 ........1 %Y A129398 This is a three-dimensional analog of A129392. %Y A129398 Cf. A129392, A129399. %K A129398 sign %O A129398 0,4 %A A129398 _Jonas Wallgren_, Apr 13 2007