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 A253009 #6 Jul 23 2025 13:51:20 %S A253009 10,85,632,3423,14795,54219,2327062,43197859,395069496,2063349297, %T A253009 7250116841,19242081848,41884052188,79190458776,135212633776, %U A253009 214009464108,319640931500,456167117868,627648109484,838143992620 %N A253009 Number of nX6 nonnegative integer arrays with upper left 0 and lower right its king-move distance away minus 3 and every value increasing by 0 or 1 with every step right, diagonally se or down. %C A253009 Column 6 of A253011 %H A253009 R. H. Hardin, <a href="/A253009/b253009.txt">Table of n, a(n) for n = 1..210</a> %F A253009 Empirical: a(n) = (2030043136/3)*n^3 - 19063373824*n^2 + (545623168640/3)*n - 587442631380 for n>15 %e A253009 Some solutions for n=6 %e A253009 ..0..0..0..0..1..1....0..0..0..0..0..1....0..0..0..0..1..1....0..0..0..0..0..1 %e A253009 ..0..0..0..0..1..1....0..0..0..1..1..1....0..0..0..0..1..1....0..0..0..0..1..1 %e A253009 ..0..0..0..0..1..1....0..0..0..1..1..2....0..0..0..1..1..1....0..0..0..0..1..1 %e A253009 ..0..1..1..1..1..1....1..1..1..1..1..2....0..1..1..1..2..2....0..0..0..1..1..2 %e A253009 ..1..1..1..1..2..2....1..1..1..1..1..2....1..1..1..1..2..2....1..1..1..1..1..2 %e A253009 ..1..1..2..2..2..2....1..1..2..2..2..2....1..1..1..1..2..2....2..2..2..2..2..2 %K A253009 nonn %O A253009 1,1 %A A253009 _R. H. Hardin_, Dec 25 2014