A250737 Number of (n+1) X (3+1) 0..1 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nonincreasing x(i,j)-x(i-1,j) in the j direction.

18, 22, 30, 46, 78, 142, 270, 526, 1038, 2062, 4110, 8206, 16398, 32782, 65550, 131086, 262158, 524302, 1048590, 2097166, 4194318, 8388622, 16777230, 33554446, 67108878, 134217742, 268435470, 536870926, 1073741838, 2147483662, 4294967310

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 3*a(n-1) - 2*a(n-2); a(n) = 2^(n+1) + 14.

Empirical g.f.: 2*x*(9 - 16*x) / ((1 - x)*(1 - 2*x)). - Colin Barker, Nov 16 2018

Example

Some solutions for n=4:
..0..1..0..0....1..0..1..1....0..0..0..0....0..0..1..1....0..0..0..0
..0..1..0..0....1..0..1..1....1..1..1..1....0..0..1..1....0..0..0..0
..0..1..0..0....1..0..1..1....1..1..1..1....0..0..1..1....0..0..0..0
..0..1..0..0....1..0..1..1....0..0..0..0....0..0..1..1....0..0..0..0
..0..1..0..0....1..0..1..1....1..1..1..1....0..0..1..1....0..0..0..0

Crossrefs

Column 3 of A250742.

Sequence in context: A296008 A049734 A096282 * A290172 A031407 A267826

Adjacent sequences: A250734 A250735 A250736 * A250738 A250739 A250740

Keyword

nonn

Author

R. H. Hardin, Nov 27 2014

Status

approved