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 A219079 #6 Jul 23 2025 00:13:07 %S A219079 1,11,47,165,625,2435,9367,35901,137865,529675,2034399,7813333, %T A219079 30009313,115260115,442689383,1700273453,6530386425,25081819099, %U A219079 96333894191,369997847365,1421082488529,5458073486883,20963291245879,80515511728413 %N A219079 Hilltop maps: number of 2Xn binary arrays indicating the locations of corresponding elements not exceeded by any horizontal, diagonal or antidiagonal neighbor in a random 0..1 2Xn array. %C A219079 Row 2 of A219078 %H A219079 R. H. Hardin, <a href="/A219079/b219079.txt">Table of n, a(n) for n = 1..210</a> %F A219079 Empirical: a(n) = 3*a(n-1) +a(n-2) +7*a(n-3) +6*a(n-4) %e A219079 Some solutions for n=3 %e A219079 ..1..1..1....1..1..0....0..1..1....1..0..1....1..1..1....0..1..1....1..1..0 %e A219079 ..1..0..0....1..0..1....0..0..0....0..1..0....0..1..0....1..0..0....1..1..0 %K A219079 nonn %O A219079 1,2 %A A219079 _R. H. Hardin_ Nov 11 2012