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 A259242 #7 Jun 02 2025 11:49:27 %S A259242 9,65,720,14425,451481,25462352,2259371001,359730429763, %T A259242 90571705672192,40745743533702439,29115984372311031043, %U A259242 37023356202692415717856,75090733417483065667600023,269938147719275944289836747059 %N A259242 Number of (n+1)X(n+1) 0..1 arrays with each 2X2 subblock having clockwise pattern 0000 0011 or 0111. %C A259242 Diagonal of A259250 %H A259242 R. H. Hardin, <a href="/A259242/b259242.txt">Table of n, a(n) for n = 1..15</a> %e A259242 Some solutions for n=4 %e A259242 ..1..1..1..1..0....0..0..1..0..0....1..1..0..0..1....0..1..0..0..1 %e A259242 ..0..0..0..1..0....1..1..1..1..1....0..1..1..1..1....1..1..1..1..1 %e A259242 ..0..0..0..1..1....1..0..1..0..0....0..1..0..1..0....1..0..1..0..1 %e A259242 ..1..1..1..1..0....1..1..1..1..1....0..1..0..1..0....1..1..1..1..1 %e A259242 ..0..1..0..1..1....1..0..0..0..1....1..1..1..1..0....1..0..0..1..0 %Y A259242 Cf. A259250 %K A259242 nonn %O A259242 1,1 %A A259242 _R. H. Hardin_, Jun 22 2015