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 A200550 #7 Jul 22 2025 15:52:04 %S A200550 80,836,7778,75792,737460,7286542,72366820,723237026,7258296910, %T A200550 73127883596,739101010202,7490787201124,76099633989974, %U A200550 774719436417776,7901415122713726,80719023935569240,825814487838111514 %N A200550 Number of -5..5 arrays x(0..n+1) of n+2 elements with zero sum and nonzero second differences. %C A200550 Column 5 of A200553 %H A200550 R. H. Hardin, <a href="/A200550/b200550.txt">Table of n, a(n) for n = 1..145</a> %e A200550 Some solutions for n=3 %e A200550 ..3....5....3....1...-3....2...-5...-1....0...-5...-4...-3...-5....0...-5....3 %e A200550 .-1....0...-2...-3....3...-4....5....5...-5...-3....3....2...-2...-3....1...-2 %e A200550 ..0...-2....1....5...-1....1...-4...-3....4....1....0...-5....2....3....4....3 %e A200550 .-3...-2....0....2....2....1....3....3....4....3...-1....1....2....2...-2...-3 %e A200550 ..1...-1...-2...-5...-1....0....1...-4...-3....4....2....5....3...-2....2...-1 %K A200550 nonn %O A200550 1,1 %A A200550 _R. H. Hardin_ Nov 19 2011