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 A207393 #7 Jul 22 2025 20:21:55 %S A207393 8,64,200,643,2356,7561,23071,72410,223804,678174,2060069,6253794, %T A207393 18886989,56994221,172026022,518680170,1563104966,4710798095, %U A207393 14194683842,42764679095,128836561789,388135277342,1169254115920,3522329560926 %N A207393 Number of 4Xn 0..1 arrays avoiding 0 0 1 and 0 1 0 horizontally and 0 0 1 and 1 1 0 vertically. %C A207393 Row 4 of A207391 %H A207393 R. H. Hardin, <a href="/A207393/b207393.txt">Table of n, a(n) for n = 1..210</a> %F A207393 Empirical: a(n) = 5*a(n-1) -8*a(n-2) +19*a(n-3) -54*a(n-4) +51*a(n-5) -64*a(n-6) +169*a(n-7) -78*a(n-8) +62*a(n-9) -265*a(n-10) +27*a(n-11) -41*a(n-12) +277*a(n-13) +16*a(n-14) +40*a(n-15) -162*a(n-16) -31*a(n-17) -10*a(n-18) +41*a(n-19) +13*a(n-20) -6*a(n-22) %e A207393 Some solutions for n=4 %e A207393 ..1..1..0..0....1..1..1..1....0..1..1..1....1..1..1..1....1..0..1..1 %e A207393 ..1..0..0..0....1..1..1..1....0..0..0..0....1..0..0..0....0..1..1..1 %e A207393 ..1..1..0..0....1..1..1..1....0..1..1..0....1..1..1..1....1..1..1..1 %e A207393 ..1..0..0..0....1..1..1..1....0..0..0..0....1..0..0..0....1..1..1..1 %K A207393 nonn %O A207393 1,1 %A A207393 _R. H. Hardin_ Feb 17 2012