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 A200450 #7 Jul 22 2025 15:49:41 %S A200450 44,342,2334,16380,115140,820650,5876818,42324384,306098316, %T A200450 2222013090,16179361028,118122171194,864377954818,6338065287424, %U A200450 46557302873890,342540516750538,2523812868946712,18619248362911724,137522653687668252 %N A200450 Number of -4..4 arrays x(0..n+1) of n+2 elements with zero sum and nonzero first and second differences. %C A200450 Column 4 of A200454 %H A200450 R. H. Hardin, <a href="/A200450/b200450.txt">Table of n, a(n) for n = 1..200</a> %e A200450 Some solutions for n=3 %e A200450 ..2...-3....4...-4...-3...-3...-1...-3....2....0....4....1....2...-4....0....4 %e A200450 ..0....1....0....4....2....3....0...-4...-3....4....0....2....1...-2....1....3 %e A200450 ..2...-4...-1...-3...-3....1...-2....4....0...-3....2....1...-4....2...-2...-4 %e A200450 .-3....4...-3...-1....0...-2....0....3...-1....2...-2...-4....3....1....2...-2 %e A200450 .-1....2....0....4....4....1....3....0....2...-3...-4....0...-2....3...-1...-1 %K A200450 nonn %O A200450 1,1 %A A200450 _R. H. Hardin_ Nov 18 2011