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 A221441 #8 Aug 05 2018 08:20:29 %S A221441 5,33,221,1473,9829,65569,437437,2918273,19468741,129882145,866485149, %T A221441 5780598081,38564209189,257274109985,1716357449085,11450366664449, %U A221441 76389039372165,509615587618849,3399807737852509,22681199192442049 %N A221441 Hilltop maps: number of n X 3 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or antidiagonal neighbor in a random 0..1 n X 3 array. %C A221441 Column 3 of A221446. %H A221441 R. H. Hardin, <a href="/A221441/b221441.txt">Table of n, a(n) for n = 1..210</a> %F A221441 Empirical: a(n) = 5*a(n-1) + 11*a(n-2) + a(n-3). %F A221441 Empirical g.f.: x*(5 + 8*x + x^2) / (1 - 5*x - 11*x^2 - x^3). - _Colin Barker_, Aug 05 2018 %e A221441 Some solutions for n=3: %e A221441 ..1..1..0....0..1..1....1..0..1....0..1..1....1..0..1....1..1..0....0..1..1 %e A221441 ..0..0..1....0..1..0....1..1..1....0..1..0....0..1..0....0..1..1....1..1..1 %e A221441 ..1..1..0....1..1..1....1..1..0....1..0..1....0..1..1....1..0..1....1..0..1 %Y A221441 Cf. A221446. %K A221441 nonn %O A221441 1,1 %A A221441 _R. H. Hardin_, Jan 17 2013