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 A206695 #7 Jul 22 2025 19:37:09 %S A206695 26,676,15712,363465,8366690,192513201,4428597297,101873060353, %T A206695 2343406014665,53905733689480,1240001271788197,28523922980667486, %U A206695 656139776848417214,15093274671338487633,347192698846268632122 %N A206695 Number of nX3 0..2 arrays avoiding the pattern z-2 z-1 z in any row or column. %C A206695 Column 3 of A206700 %H A206695 R. H. Hardin, <a href="/A206695/b206695.txt">Table of n, a(n) for n = 1..210</a> %F A206695 Empirical: a(n) = 29*a(n-1) -84*a(n-2) -1570*a(n-3) +6618*a(n-4) +28026*a(n-5) -136815*a(n-6) -145173*a(n-7) +1005714*a(n-8) -486446*a(n-9) -1842056*a(n-10) +1805556*a(n-11) +1069186*a(n-12) -1763040*a(n-13) +27675*a(n-14) +626313*a(n-15) -148782*a(n-16) -66294*a(n-17) +19454*a(n-18) +2708*a(n-19) -849*a(n-20) -37*a(n-21) +12*a(n-22) %e A206695 Some solutions for n=4 %e A206695 ..2..2..0....2..2..1....2..0..2....0..0..2....2..1..2....1..2..1....2..2..2 %e A206695 ..0..0..2....2..0..0....1..1..1....0..0..2....1..2..1....1..1..1....1..2..1 %e A206695 ..2..0..0....2..0..0....1..0..0....0..0..0....0..2..1....1..0..1....0..2..2 %e A206695 ..1..0..1....2..2..2....1..2..2....1..2..0....1..1..2....2..1..2....0..0..2 %K A206695 nonn %O A206695 1,1 %A A206695 _R. H. Hardin_ Feb 11 2012