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 A221067 #6 Jul 23 2025 01:40:21 %S A221067 8,20,512,4096,26976,262144,2097152,16401664,134217728,1073741824, %T A221067 8572235776,68719476736,549755813888,4397319143424,35184372088832, %U A221067 281474976710656,2251771635433472,18014398509481984,144115188075855872 %N A221067 Sum of neighbor maps: number of nX3 binary arrays indicating the locations of corresponding elements equal to the sum mod 4 of their king-move neighbors in a random 0..3 nX3 array. %C A221067 Column 3 of A221072 %H A221067 R. H. Hardin, <a href="/A221067/b221067.txt">Table of n, a(n) for n = 1..210</a> %F A221067 Empirical: a(n) = 8*a(n-1) +160*a(n-3) -1280*a(n-4) -11200*a(n-6) +89600*a(n-7) +453632*a(n-9) -3629056*a(n-10) -11841536*a(n-12) +94732288*a(n-13) +209715200*a(n-15) -1677721600*a(n-16) -2577661952*a(n-18) +20621295616*a(n-19) +22041067520*a(n-21) -176328540160*a(n-22) -128781910016*a(n-24) +1030255280128*a(n-25) +490700013568*a(n-27) -3925600108544*a(n-28) -1099511627776*a(n-30) +8796093022208*a(n-31) +1099511627776*a(n-33) -8796093022208*a(n-34) %e A221067 Some solutions for n=3 %e A221067 ..0..0..0....0..0..1....1..1..0....1..1..0....1..0..1....1..0..0....0..1..0 %e A221067 ..1..0..0....0..1..1....0..1..0....1..1..1....0..1..0....0..1..1....1..0..0 %e A221067 ..1..1..1....1..1..1....0..1..0....1..1..1....1..0..0....0..1..0....1..0..1 %K A221067 nonn %O A221067 1,1 %A A221067 _R. H. Hardin_ Dec 31 2012