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 A198713 #7 Jul 22 2025 13:05:33 %S A198713 41,8404,1749965,364637102,75987485516,15835552812749, %T A198713 3300094936852775,687733321797971342,143322307142433346196, %U A198713 29868095632655586533219,6224454258216624967544685,1297164418016611898106044912 %N A198713 Number of nX6 0..3 arrays with values 0..3 introduced in row major order and no element equal to any horizontal or vertical neighbor. %C A198713 Column 6 of A198715 %H A198713 R. H. Hardin, <a href="/A198713/b198713.txt">Table of n, a(n) for n = 1..200</a> %F A198713 Empirical: a(n) = 313*a(n-1) -25836*a(n-2) +915863*a(n-3) -16213670*a(n-4) +144756201*a(n-5) -517271096*a(n-6) -1142631169*a(n-7) +16130100519*a(n-8) -49834494904*a(n-9) +41222570902*a(n-10) +81411834252*a(n-11) -186980689770*a(n-12) +120589827444*a(n-13) -21008679048*a(n-14) %e A198713 Some solutions with all values from 0 to 3 for n=4 %e A198713 ..0..1..0..1..0..2....0..1..0..2..3..0....0..1..0..2..0..3....0..1..0..2..1..2 %e A198713 ..1..0..2..3..2..3....1..0..2..0..1..2....1..0..2..0..1..2....1..0..2..0..2..3 %e A198713 ..0..1..0..2..3..2....0..1..0..2..0..3....0..1..0..1..0..3....0..1..0..1..0..2 %e A198713 ..1..0..1..3..1..3....1..0..3..0..2..0....1..0..2..0..3..2....1..0..3..2..1..3 %K A198713 nonn %O A198713 1,1 %A A198713 _R. H. Hardin_ Oct 29 2011