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 A208201 #7 Jul 22 2025 21:14:46 %S A208201 1,2,2,5,14,5,15,178,178,15,51,2653,10366,2653,51,187,41272,639701, %T A208201 639701,41272,187,715,648569,39725054,156617480,39725054,648569,715, %U A208201 2795,10215440,2468504665,38372808893,38372808893,2468504665,10215440,2795 %N A208201 T(n,k)=Number of nXk 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than two of its immediate leftward or upward or left-upward diagonal neighbors. %C A208201 Table starts %C A208201 ....1.........2.............5.................15......................51 %C A208201 ....2........14...........178...............2653...................41272 %C A208201 ....5.......178.........10366.............639701................39725054 %C A208201 ...15......2653........639701..........156617480.............38372808893 %C A208201 ...51.....41272......39725054........38372808893..........37069738362057 %C A208201 ..187....648569....2468504665......9402035642924.......35810971705853725 %C A208201 ..715..10215440..153402542384...2303673397508915....34594950233928279876 %C A208201 .2795.160984657.9533100532733.564442821781056268.33420220819293699707599 %H A208201 R. H. Hardin, <a href="/A208201/b208201.txt">Table of n, a(n) for n = 1..220</a> %e A208201 Some solutions for n=4 k=3 %e A208201 ..0..0..1....0..0..0....0..1..1....0..0..0....0..1..1....0..0..0....0..1..0 %e A208201 ..0..2..0....0..1..1....0..0..0....1..1..0....1..0..0....0..1..2....0..2..3 %e A208201 ..1..2..1....2..0..2....0..1..1....0..1..0....0..1..0....1..1..3....3..0..0 %e A208201 ..3..0..0....2..1..0....0..2..1....0..1..0....1..0..0....1..0..0....2..1..3 %Y A208201 Column 1 is A007581(n-1) %K A208201 nonn,tabl %O A208201 1,2 %A A208201 _R. H. Hardin_ Feb 24 2012