A250777 Number of (n+1) X (2+1) 0..1 arrays with nondecreasing x(i,j)+x(i,j-1) in the i direction and nondecreasing absolute value of x(i,j)-x(i-1,j) in the j direction.

21, 46, 96, 196, 396, 796, 1596, 3196, 6396, 12796, 25596, 51196, 102396, 204796, 409596, 819196, 1638396, 3276796, 6553596, 13107196, 26214396, 52428796, 104857596, 209715196, 419430396, 838860796, 1677721596, 3355443196

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) = 25*2^(n-1) - 4.

Empirical g.f.: x*(21 - 17*x) / ((1 - x)*(1 - 2*x)). - Colin Barker, Nov 19 2018

Example

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

Crossrefs

Column 2 of A250783.

Sequence in context: A044098 A044479 A139581 * A327302 A156966 A146705

Adjacent sequences: A250774 A250775 A250776 * A250778 A250779 A250780

Keyword

nonn

Author

R. H. Hardin, Nov 27 2014

Status

approved