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 A207496 #7 Jul 22 2025 20:30:07 %S A207496 9,81,283,1004,3939,15495,62530,253747,1040401,4290258,17800079, %T A207496 74193193,310541536,1304248843,5493846571,23198279836,98159361513, %U A207496 416061031363,1766079438934,7505644908143,31930399614415,135952464116764 %N A207496 Number of nX4 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 1 and 1 0 0 vertically. %C A207496 Column 4 of A207500 %H A207496 R. H. Hardin, <a href="/A207496/b207496.txt">Table of n, a(n) for n = 1..210</a> %F A207496 Empirical: a(n) = 9*a(n-1) -11*a(n-2) -92*a(n-3) +184*a(n-4) +391*a(n-5) -806*a(n-6) -893*a(n-7) +1570*a(n-8) +1170*a(n-9) -1486*a(n-10) -867*a(n-11) +679*a(n-12) +340*a(n-13) -139*a(n-14) -62*a(n-15) +10*a(n-16) +4*a(n-17) for n>18 %e A207496 Some solutions for n=4 %e A207496 ..0..0..1..0....1..1..0..1....1..0..1..0....0..1..0..0....1..1..0..1 %e A207496 ..1..0..1..0....1..1..0..1....0..0..1..0....0..0..1..0....0..1..0..0 %e A207496 ..0..0..1..0....0..1..0..0....1..0..1..0....0..1..0..0....1..1..0..1 %e A207496 ..1..0..1..0....1..0..0..1....0..0..1..0....0..0..1..0....0..1..0..1 %K A207496 nonn %O A207496 1,1 %A A207496 _R. H. Hardin_ Feb 18 2012