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 A297726 #4 Jan 04 2018 22:03:37 %S A297726 1,2735,110551,2139403,91994155,4238895126,154327332017,5699564719228, %T A297726 225335188630385,8767500946143576,335583072729414460, %U A297726 12937974222045436776,500589141612794916455,19317070336607603879897 %N A297726 Number of 7Xn 0..1 arrays with every 1 horizontally, diagonally or antidiagonally adjacent to 1, 2 or 4 neighboring 1s. %C A297726 Row 7 of A297720. %H A297726 R. H. Hardin, <a href="/A297726/b297726.txt">Table of n, a(n) for n = 1..210</a> %e A297726 Some solutions for n=3 %e A297726 ..1..0..1. .0..0..0. .1..0..0. .0..1..1. .0..0..0. .1..0..0. .0..1..0 %e A297726 ..0..1..0. .0..1..1. .0..1..1. .1..0..0. .1..1..0. .1..1..0. .0..1..1 %e A297726 ..0..0..0. .0..1..0. .0..0..0. .1..1..0. .1..1..0. .0..0..0. .0..0..1 %e A297726 ..0..1..1. .0..0..0. .1..1..0. .1..0..1. .1..0..1. .1..1..1. .0..1..1 %e A297726 ..0..0..0. .0..1..1. .0..0..0. .1..0..0. .0..1..0. .0..0..0. .0..0..0 %e A297726 ..1..1..1. .1..1..0. .1..1..0. .0..1..0. .0..1..0. .1..0..1. .0..0..1 %e A297726 ..0..0..0. .0..0..0. .0..1..0. .1..0..0. .1..1..1. .0..1..0. .1..1..0 %Y A297726 Cf. A297720. %K A297726 nonn %O A297726 1,2 %A A297726 _R. H. Hardin_, Jan 04 2018