cp's OEIS Frontend

A221442 Hilltop maps: number of n X 4 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or antidiagonal neighbor in a random 0..1 n X 4 array.

%I A221442 #8 Aug 05 2018 08:20:23
%S A221442 9,117,1465,18393,230845,2897357,36364977,456419681,5728560373,
%T A221442 71899621813,902417942313,11326320232169,142157556964077,
%U A221442 1784230940565533,22394026158604769,281069224947245681
%N A221442 Hilltop maps: number of n X 4 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or antidiagonal neighbor in a random 0..1 n X 4 array.
%C A221442 Column 4 of A221446.
%H A221442 R. H. Hardin, <a href="/A221442/b221442.txt">Table of n, a(n) for n = 1..210</a>
%F A221442 Empirical: a(n) = 9*a(n-1) + 42*a(n-2) + 34*a(n-3) - 21*a(n-4) - 11*a(n-5) - 4*a(n-6).
%F A221442 Empirical g.f.: x*(9 + 36*x + 34*x^2 - 12*x^3 - 11*x^4 - 8*x^5) / (1 - 9*x - 42*x^2 - 34*x^3 + 21*x^4 + 11*x^5 + 4*x^6). - _Colin Barker_, Aug 05 2018
%e A221442 Some solutions for n=3:
%e A221442 ..1..1..0..0....0..1..0..1....1..1..1..1....1..0..0..1....0..1..0..0
%e A221442 ..1..1..1..0....1..0..0..1....1..0..1..1....1..0..0..0....0..0..1..0
%e A221442 ..1..0..1..1....1..1..1..0....0..1..1..0....1..1..1..0....1..0..1..1
%Y A221442 Cf. A221446.
%K A221442 nonn
%O A221442 1,1
%A A221442 _R. H. Hardin_, Jan 17 2013