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 A200448 #9 Jul 22 2025 15:49:28 %S A200448 10,44,144,486,1582,5478,18692,64782,223272,776430,2701660,9439702, %T A200448 33021250,115801892,406698282,1430840312,5040451088,17779563894, %U A200448 62784860258,221948186878,785340477204,2781302241584,9857972484436 %N A200448 Number of -2..2 arrays x(0..n+1) of n+2 elements with zero sum and nonzero first and second differences. %C A200448 Column 2 of A200454 %H A200448 R. H. Hardin, <a href="/A200448/b200448.txt">Table of n, a(n) for n = 1..200</a> %e A200448 Some solutions for n=3 %e A200448 .-1...-1...-2....1...-1....2....2...-2....2....2....1....1....1...-2...-2....0 %e A200448 ..2....1....1....0....1...-1...-1....2...-2...-1...-2...-2...-1....1....1....1 %e A200448 .-1...-2....2...-2....2....1....0....0....0...-2....1....2....0....2...-1...-1 %e A200448 ..2....2....0....2...-2....0...-2...-1...-1....0....2...-1....2...-1....2....1 %e A200448 .-2....0...-1...-1....0...-2....1....1....1....1...-2....0...-2....0....0...-1 %K A200448 nonn %O A200448 1,1 %A A200448 _R. H. Hardin_ Nov 18 2011