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 A203356 #9 Jul 22 2025 17:10:36 %S A203356 1,7,102,5677,984703,572818585,1089970014327,6842701992875869, %T A203356 141313097261182627960,9609805102278645983838526, %U A203356 2151172274505675499995093835341,1585313606427874519807992162372572320 %N A203356 Number of n X n binary arrays with every 1 immediately preceded by 0 to the left or above. %C A203356 Diagonal of A203362 %H A203356 R. H. Hardin, <a href="/A203356/b203356.txt">Table of n, a(n) for n = 1..22</a> %e A203356 Some solutions for n=4 %e A203356 ..0..0..1..0....0..1..0..1....0..0..1..0....0..1..0..0....0..1..0..0 %e A203356 ..0..1..0..1....0..1..1..0....0..0..0..1....0..1..0..1....0..1..0..1 %e A203356 ..0..0..0..0....0..0..0..1....1..0..0..1....0..1..0..0....0..0..0..1 %e A203356 ..1..1..0..0....0..1..0..1....0..1..1..0....0..0..0..1....0..0..1..0 %K A203356 nonn %O A203356 1,2 %A A203356 _R. H. Hardin_ Dec 31 2011