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 A207404 #7 Jul 22 2025 20:22:46 %S A207404 8,64,216,729,1782,4356,8910,18225,33210,60516,101598,170569,269276, %T A207404 425104,639612,962361,1393020,2016400,2827220,3964081,5411538,7387524, %U A207404 9858186,13155129,17213742,22524516,28974330,37271025,47228280,59845696 %N A207404 Number of 4Xn 0..1 arrays avoiding 0 0 1 and 0 1 1 horizontally and 0 0 1 and 1 1 0 vertically. %C A207404 Row 4 of A207403 %H A207404 R. H. Hardin, <a href="/A207404/b207404.txt">Table of n, a(n) for n = 1..210</a> %F A207404 Empirical: a(n) = 2*a(n-1) +6*a(n-2) -14*a(n-3) -14*a(n-4) +42*a(n-5) +14*a(n-6) -70*a(n-7) +70*a(n-9) -14*a(n-10) -42*a(n-11) +14*a(n-12) +14*a(n-13) -6*a(n-14) -2*a(n-15) +a(n-16) %e A207404 Some solutions for n=4 %e A207404 ..0..1..0..0....0..0..0..0....1..0..0..0....1..1..0..1....1..0..0..0 %e A207404 ..0..0..0..0....0..0..0..0....0..1..0..0....1..0..1..0....0..1..0..0 %e A207404 ..0..0..0..0....0..0..0..0....1..0..0..0....1..0..0..0....1..1..0..0 %e A207404 ..0..0..0..0....0..0..0..0....1..1..0..0....1..0..0..0....0..1..0..0 %K A207404 nonn %O A207404 1,1 %A A207404 _R. H. Hardin_ Feb 17 2012