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 A206879 #7 Oct 18 2021 17:07:43 %S A206879 12,144,1011,6478,44879,321393,2276625,15986104,112334542,790951091, %T A206879 5570201912,39212133425,276007394747,1942896002325,13677110916246, %U A206879 96279937841588,677755568854937,4771010567436598,33585249323714265 %N A206879 Number of n X 4 0..1 arrays avoiding 0 1 0 horizontally and 1 0 1 vertically. %C A206879 Column 4 of A206883. %H A206879 R. H. Hardin, <a href="/A206879/b206879.txt">Table of n, a(n) for n = 1..210</a> %F A206879 Empirical: a(n) = 8*a(n-1) -18*a(n-2) +69*a(n-3) +92*a(n-4) -189*a(n-5) +404*a(n-6) -187*a(n-7) -4014*a(n-8) -682*a(n-9) +9084*a(n-10) +5101*a(n-11) -6052*a(n-12) -5594*a(n-13) -1393*a(n-14) -277*a(n-15) +1312*a(n-16) +1153*a(n-17) +533*a(n-18) +112*a(n-19) -87*a(n-20) -46*a(n-21) -32*a(n-22) -9*a(n-23) +3*a(n-24) +a(n-25). %e A206879 Some solutions for n=4 %e A206879 ..0..0..1..1....0..1..1..0....0..1..1..0....1..0..0..1....1..0..0..0 %e A206879 ..1..1..0..1....0..1..1..1....0..1..1..1....1..1..0..0....0..1..1..0 %e A206879 ..1..0..0..0....1..0..0..1....0..1..1..1....1..0..0..0....0..0..1..1 %e A206879 ..0..0..0..0....1..0..0..0....1..0..1..1....1..0..0..1....1..0..1..1 %Y A206879 Cf. A206883. %K A206879 nonn %O A206879 1,1 %A A206879 _R. H. Hardin_, Feb 13 2012