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 A200547 #12 Aug 24 2025 11:24:15 %S A200547 14,76,280,1240,4978,21626,91058,393660,1686980,7309386,31632968, %T A200547 137600876,599055566,2615427970,11433493630,50075195034,219589525108, %U A200547 964264276780,4238966033150,18655002576606,82175337524524,362306822490256,1598684706408864,7059561038745824 %N A200547 Number of -2..2 arrays x(0..n+1) of n+2 elements with zero sum and nonzero second differences. %H A200547 R. H. Hardin, <a href="/A200547/b200547.txt">Table of n, a(n) for n = 1..200</a> %e A200547 Some solutions for n=3: %e A200547 ..2....1....0....0...-2...-1....1....0....0....1...-2...-2...-1....0...-1....2 %e A200547 ..0...-1....2...-2....1....1....0....2...-2....1....1...-1....2....0...-1...-1 %e A200547 .-1....1...-1....0...-1....0...-2...-2....2...-2....1....1....2...-1....1...-2 %e A200547 .-1...-1...-1....0....1....2...-1...-2...-1....2....0....0...-1....2....2....0 %e A200547 ..0....0....0....2....1...-2....2....2....1...-2....0....2...-2...-1...-1....1 %Y A200547 Column 2 of A200553. %K A200547 nonn,changed %O A200547 1,1 %A A200547 _R. H. Hardin_, Nov 19 2011