A224311 Number of 3Xn 0..2 arrays with diagonals and rows unimodal and antidiagonals nondecreasing.

27, 324, 1586, 5996, 20214, 61953, 174378, 454832, 1108958, 2547780, 5554847, 11564081, 23107746, 44519456, 83011127, 150287312, 264917825, 455762696, 766835415, 1264104630, 2044874898, 3250558135, 5083853932, 7831604260

Offset: 1

Author

R. H. Hardin Apr 03 2013

Keywords

• nonn

Comments

Row 3 of A224310

Examples

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

Links

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

Formula

Empirical: a(n) = (1/19160064)*n^12 + (1/1064448)*n^11 + (1507/43545600)*n^10 + (73/161280)*n^9 + (23603/2903040)*n^8 + (111/3584)*n^7 + (13023121/43545600)*n^6 + (130093/96768)*n^5 + (5619469/2177280)*n^4 + (54895/2688)*n^3 - (11456441/1663200)*n^2 + (205131/1540)*n - 196 for n>3