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 A208711 #7 Jul 22 2025 21:29:19 %S A208711 8,128,1372,16084,185344,2142580,24754628,286034292,3305009328, %T A208711 38188137788,441249345280,5098468022268,58910854227068, %U A208711 680692462409636,7865141904908344,90878716312611076,1050068921631026592 %N A208711 Number of 4Xn 0..1 arrays with new values 0..1 introduced in row major order and no element equal to more than two of its immediate leftward or upward or right-upward antidiagonal neighbors. %C A208711 Row 4 of A208709 %H A208711 R. H. Hardin, <a href="/A208711/b208711.txt">Table of n, a(n) for n = 1..210</a> %F A208711 Empirical: a(n) = 9*a(n-1) +31*a(n-2) -11*a(n-3) -71*a(n-4) -a(n-5) +38*a(n-6) -8*a(n-7) for n>9 %e A208711 Some solutions for n=4 %e A208711 ..0..1..0..1....0..1..0..1....0..1..1..0....0..0..0..1....0..0..0..1 %e A208711 ..1..0..1..1....1..1..0..1....0..0..1..0....1..0..1..1....1..0..0..0 %e A208711 ..0..0..0..1....0..1..1..0....0..0..1..1....0..0..1..0....1..1..1..1 %e A208711 ..0..1..0..1....0..0..1..1....1..0..0..0....0..1..0..0....1..0..1..1 %K A208711 nonn %O A208711 1,1 %A A208711 _R. H. Hardin_ Mar 01 2012