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 A204706 #8 Jul 22 2025 18:15:01 %S A204706 7,33,257,3473,73345,2542369,140090241,12503757969,1787244586881, %T A204706 411927241028353,152442345546739969,90819596095626887105, %U A204706 86960426240537811217921,133963874202574308172821153 %N A204706 Number of (n+1)X(n+1) 0..1 arrays with the permanents of all 2X2 subblocks equal and nonzero. %C A204706 Diagonal of A204713 %H A204706 R. H. Hardin, <a href="/A204706/b204706.txt">Table of n, a(n) for n = 1..19</a> %e A204706 Some solutions for n=4 %e A204706 ..0..1..0..1..1....0..1..0..1..1....1..0..1..1..1....0..1..0..1..0 %e A204706 ..1..0..1..1..0....1..1..1..0..1....0..1..1..0..1....1..0..1..1..1 %e A204706 ..1..1..0..1..1....0..1..0..1..0....1..1..0..1..0....0..1..0..1..0 %e A204706 ..0..1..1..1..0....1..1..1..1..1....1..0..1..1..1....1..1..1..1..1 %e A204706 ..1..0..1..0..1....1..0..1..0..1....0..1..1..0..1....0..1..0..1..0 %K A204706 nonn %O A204706 1,1 %A A204706 _R. H. Hardin_ Jan 18 2012