A102864 Leading column of A102416.
2, 2, 4, 16, 28, 56, 108, 216, 424, 848, 1684, 3368, 6712, 13424, 26808, 53616, 107152, 214304, 428460, 856920, 1713544, 3427088
Offset: 0
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.
Triangle begins: .1 .1,1 .0,2,0 .0,2,2,0 .0,2,2,2,0 .0,2,4,4,2,0 .0,2,4,8,4,2,0
U:=proc(n,k) option remember; if n < 1 then RETURN(0); fi; if n = 1 then RETURN(1); fi; if n > 1 and k = 0 then RETURN(0); fi; if k > 1 and k >= n then RETURN(0); fi; U(n-1,k)+U(n-1,k-1)-E(n,k); end; E:=proc(n,k) option remember; if n mod 2 = 0 and k mod 2 = 0 then U(n/2,k/2) else 0; fi; end;