A250995 Number of (1+1) X (n+1) 0..2 arrays with nondecreasing min(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.

40, 169, 646, 2359, 8298, 28450, 95628, 316568, 1035294, 3352547, 10768211, 34351193, 108947285, 343813542, 1080310949, 3381653079, 10550153029, 32817177900, 101810982442, 315106120063, 973171192417, 2999712678334

Offset

1,1

Links

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

Formula

Empirical: a(n) = 6*a(n-1) - 7*a(n-2) - 12*a(n-3) + 15*a(n-4) + 11*a(n-5) - 5*a(n-6) - 3*a(n-7).

Empirical g.f.: x*(40 - 71*x - 88*x^2 + 146*x^3 + 94*x^4 - 48*x^5 - 27*x^6) / ((1 + x)*(1 - 3*x)*(1 - x - x^2)*(1 - 3*x + x^3)). - Colin Barker, Nov 24 2018

Example

Some solutions for n=4:
  1 2 0 2 1     0 1 1 0 1     1 0 2 0 0     0 2 0 0 2
  1 2 0 2 1     0 1 1 0 1     1 0 2 1 2     0 2 2 2 0

Crossrefs

Row 1 of A250994.

Sequence in context: A205249 A211155 A250994 * A262487 A322774 A264547

Adjacent sequences: A250992 A250993 A250994 * A250996 A250997 A250998

Keyword

nonn

Author

R. H. Hardin, Nov 29 2014

Status

approved