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 A298088 #6 May 03 2020 15:43:10 %S A298088 0,3,15,30,45,171,229,417,822,1359,1993,5049,3669,7878,33158,16734, %T A298088 37752,734240,160344,389218,50665319,1735920,6661033 %N A298088 Number of n X n 0..1 arrays with every element equal to 1, 2, 4 or 7 king-move adjacent elements, with upper left element zero. %C A298088 Diagonal of A298093. %e A298088 Some solutions for n=7 %e A298088 ..0..0..1..0..1..0..1. .0..0..1..0..0..1..1. .0..1..1..0..0..0..0 %e A298088 ..1..1..0..1..0..1..0. .1..0..1..1..1..0..0. .1..0..0..1..1..1..1 %e A298088 ..1..0..1..0..1..0..1. .1..1..1..0..0..0..1. .0..1..0..0..0..0..0 %e A298088 ..1..1..1..0..0..0..1. .0..0..0..1..1..0..1. .0..1..0..1..1..1..1 %e A298088 ..1..1..1..0..0..0..1. .1..1..1..1..0..0..1. .0..1..0..0..0..0..0 %e A298088 ..1..0..1..0..1..0..1. .0..0..0..1..0..0..1. .1..0..0..1..1..1..1 %e A298088 ..0..0..1..1..1..0..0. .1..1..1..0..1..1..0. .0..1..1..0..0..0..0 %Y A298088 Cf. A298093. %K A298088 nonn %O A298088 1,2 %A A298088 _R. H. Hardin_, Jan 12 2018