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 A200453 #7 Jun 07 2021 13:59:14 %S A200453 142,1832,22276,278906,3513884,44716536,572857272,7380022092, %T A200453 95496980144,1240352594210,16161267003100,211148128583658, %U A200453 2765181621011902,36287540439791446,477071904597059874,6282247056373911518 %N A200453 Number of -7..7 arrays x(0..n+1) of n+2 elements with zero sum and nonzero first and second differences. %C A200453 Column 7 of A200454. %H A200453 R. H. Hardin, <a href="/A200453/b200453.txt">Table of n, a(n) for n = 1..97</a> %e A200453 Some solutions for n=3 %e A200453 .-1...-4....0....7....5....5....6...-4....2....0...-1...-5....4....2...-6...-6 %e A200453 .-3....3....2....0...-1....2...-2....6....3....4....2....6...-5....3...-1....7 %e A200453 ..4....4...-5...-1...-2...-6...-4....4...-5...-1...-3....1....1...-4....1...-6 %e A200453 .-5...-3....3...-4...-4...-4...-7....0...-1...-4....4...-5...-3....3....6....2 %e A200453 ..5....0....0...-2....2....3....7...-6....1....1...-2....3....3...-4....0....3 %K A200453 nonn %O A200453 1,1 %A A200453 _R. H. Hardin_ Nov 18 2011