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 A220802 #6 Jul 24 2025 19:40:45 %S A220802 8,48,512,4096,30766,262144,2097152,16728064,134217728,1073741824, %T A220802 8587150368,68719476736,549755813888,4397962625024,35184372088832, %U A220802 281474976710656,2251796346117248,18014398509481984,144115188075855872 %N A220802 Sum of neighbor maps: number of nX3 binary arrays indicating the locations of corresponding elements equal to the sum mod 4 of their horizontal and vertical neighbors in a random 0..3 nX3 array. %C A220802 Column 3 of A220805 %H A220802 R. H. Hardin, <a href="/A220802/b220802.txt">Table of n, a(n) for n = 1..146</a> %e A220802 Some solutions for n=3 %e A220802 ..1..0..1....0..1..0....1..0..1....1..0..1....0..1..0....0..0..1....0..0..1 %e A220802 ..1..1..1....0..1..1....0..1..0....1..1..1....1..0..1....0..0..0....1..1..0 %e A220802 ..0..1..1....1..1..1....1..1..0....0..0..1....1..0..0....1..1..1....0..1..1 %K A220802 nonn %O A220802 1,1 %A A220802 _R. H. Hardin_ Dec 21 2012