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 A298890 #4 Jan 28 2018 09:03:11 %S A298890 0,3,1,4,4,11,26,66,171,462,1248,3419,9450,26334,73697,206960,582316, %T A298890 1640549,4625476,13047636,36816651,103906694,293290860,827923703, %U A298890 2337253142,6598367806,18628473233,52592572696,148482655256,419208157101 %N A298890 Number of nX3 0..1 arrays with every element equal to 2, 3, 5, 6 or 8 king-move adjacent elements, with upper left element zero. %C A298890 Column 3 of A298895. %H A298890 R. H. Hardin, <a href="/A298890/b298890.txt">Table of n, a(n) for n = 1..210</a> %F A298890 Empirical: a(n) = 4*a(n-1) -a(n-2) -5*a(n-3) -10*a(n-4) +11*a(n-5) +15*a(n-6) +2*a(n-7) -5*a(n-8) -33*a(n-9) -20*a(n-10) +47*a(n-11) +36*a(n-12) +4*a(n-14) -12*a(n-15) -2*a(n-16) +2*a(n-17) for n>18 %e A298890 Some solutions for n=7 %e A298890 ..0..0..0. .0..0..1. .0..0..0. .0..0..0. .0..1..1. .0..0..0. .0..1..1 %e A298890 ..0..0..0. .0..1..1. .0..0..0. .0..0..0. .0..0..1. .1..0..1. .0..0..1 %e A298890 ..1..1..1. .1..0..0. .0..0..0. .1..1..1. .1..0..1. .1..1..1. .1..0..1 %e A298890 ..0..1..0. .1..0..1. .0..0..0. .1..1..1. .1..1..0. .0..0..1. .1..1..0 %e A298890 ..0..0..0. .1..1..1. .1..1..1. .0..0..0. .1..0..1. .0..1..0. .0..0..0 %e A298890 ..0..1..0. .1..0..1. .1..1..1. .0..0..0. .0..0..1. .1..1..0. .0..1..0 %e A298890 ..1..1..1. .0..0..0. .1..1..1. .0..0..0. .0..1..1. .1..0..0. .1..1..1 %Y A298890 Cf. A298895. %K A298890 nonn %O A298890 1,2 %A A298890 _R. H. Hardin_, Jan 28 2018