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 A249986 #7 Nov 10 2018 09:08:52 %S A249986 466,7138,43068,168506,508902,1290856,2886016,5862924,11046810, %T A249986 19587334,33034276,53421174,83356910,126125244,185792296,267321976, %U A249986 376699362,521062026,708839308,949899538,1255705206,1639476080,2116360272 %N A249986 Number of length 6+1 0..2*n arrays with the sum of the absolute values of adjacent differences equal to 6*n. %H A249986 R. H. Hardin, <a href="/A249986/b249986.txt">Table of n, a(n) for n = 1..210</a> %F A249986 Empirical: a(n) = (1987/180)*n^6 + (2033/30)*n^5 + (2785/18)*n^4 + 226*n^3 - (3017/180)*n^2 + (697/30)*n. %F A249986 Conjectures from _Colin Barker_, Nov 10 2018: (Start) %F A249986 G.f.: 2*x*(233 + 1938*x + 1444*x^2 + 309*x^3 + 134*x^4 - 84*x^5) / (1 - x)^7. %F A249986 a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7. %F A249986 (End) %e A249986 Some solutions for n=4: %e A249986 ..5....0....0....5....2....4....2....5....2....0....0....3....0....0....1....5 %e A249986 ..2....5....7....0....8....7....4....0....1....1....3....0....2....2....7....1 %e A249986 ..0....0....1....6....6....1....0....7....7....6....6....8....7....0....2....5 %e A249986 ..8....0....3....8....1....6....6....8....0....8....4....8....1....4....0....2 %e A249986 ..0....4....4....8....5....0....0....5....3....2....8....1....3....6....0....5 %e A249986 ..2....8....8....0....7....3....5....0....5....6....1....7....6....0....7....8 %e A249986 ..3....2....4....3....2....2....4....3....0....0....6....7....0....8....3....1 %Y A249986 Row 6 of A249982. %K A249986 nonn %O A249986 1,1 %A A249986 _R. H. Hardin_, Nov 10 2014