A201974 Number of n X n 0..3 arrays with rows and columns lexicographically nondecreasing read forwards and nonincreasing read backwards.

4, 30, 1372, 408599, 858105364, 13486744809160, 1716349328902123738

Offset

1,1

Comments

Diagonal of A201981.

Links

Table of n, a(n) for n=1..7.

Example

Some solutions for n=3
..0..3..3....0..0..2....2..3..3....0..2..2....1..2..2....0..2..3....0..1..2
..0..3..3....2..3..0....3..1..2....1..0..2....3..0..2....1..0..3....2..1..1
..3..2..2....3..2..0....3..3..0....3..3..0....3..2..0....2..1..0....3..2..0

Crossrefs

Cf. A201981.

Sequence in context: A337969 A234566 A365366 * A376765 A221250 A119926

Adjacent sequences: A201971 A201972 A201973 * A201975 A201976 A201977

Keyword

nonn

Author

R. H. Hardin, Dec 07 2011

Status

approved