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 A200546 #8 Jul 22 2025 15:51:37 %S A200546 4,14,26,72,142,362,778,1938,4366,10628,24532,59138,138680,333014, %T A200546 788374,1890870,4503208,10803262,25831504,62025512,148725902, %U A200546 357516682,859055042,2067463940,4975921904,11988835382,28892947100,69685951942 %N A200546 Number of -1..1 arrays x(0..n+1) of n+2 elements with zero sum and nonzero second differences. %C A200546 Column 1 of A200553 %H A200546 R. H. Hardin, <a href="/A200546/b200546.txt">Table of n, a(n) for n = 1..200</a> %e A200546 Some solutions for n=3 %e A200546 ..0....1...-1...-1...-1....0....1...-1....1....0....1....0...-1....1....0....1 %e A200546 .-1....1...-1....1....1...-1....1....1...-1....1....0...-1....0...-1....1...-1 %e A200546 .-1...-1....1...-1....0....1...-1....1....0...-1....1....1....0....1...-1...-1 %e A200546 ..1....0....0....1....1....1...-1...-1...-1...-1...-1....0....1...-1....1....1 %e A200546 ..1...-1....1....0...-1...-1....0....0....1....1...-1....0....0....0...-1....0 %K A200546 nonn %O A200546 1,1 %A A200546 _R. H. Hardin_ Nov 19 2011