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 A183815 #6 Dec 26 2023 23:56:36 %S A183815 512,65640,8231592,1042063656,131467169720,16607782066704, %T A183815 2096961683069192,264820293988996048,33441129238755694072, %U A183815 4223013161022170839808,533285078101618075961512 %N A183815 1/81 the number of (n+1) X 5 0..2 arrays with no 2 X 2 subblock being a reflection across the shared element pair of any horizontal or vertical neighbor. %C A183815 Column 4 of A183819. %e A183815 Some solutions with upper left block zero for 3 X 5 %e A183815 ..0..0..2..0..2....0..0..1..1..2....0..0..1..2..0....0..0..2..2..2 %e A183815 ..0..0..2..2..1....0..0..2..1..2....0..0..1..2..1....0..0..2..1..1 %e A183815 ..0..1..1..2..0....0..2..0..0..1....2..1..1..1..2....0..1..1..0..0 %Y A183815 Cf. A183819. %K A183815 nonn %O A183815 1,1 %A A183815 _R. H. Hardin_, Jan 07 2011