A224375 Number of 3Xn 0..2 arrays with rows unimodal and antidiagonals nondecreasing.

27, 324, 1838, 7608, 26314, 80819, 227112, 593400, 1455898, 3378085, 7455007, 15725041, 31840088, 62123439, 117194882, 214407666, 381424761, 661365902, 1120086056, 1856304530, 3015496746, 4808693047, 7537606592, 11627841824

Offset: 1

Author

R. H. Hardin Apr 05 2013

Keywords

• nonn

Comments

Row 3 of A224374

Examples

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

Links

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

Formula

Empirical: a(n) = (1/19160064)*n^12 + (1/456192)*n^11 + (2287/43545600)*n^10 + (215/290304)*n^9 + (20603/2903040)*n^8 + (923/17920)*n^7 + (14627101/43545600)*n^6 + (400091/207360)*n^5 + (16965289/2177280)*n^4 + (3069023/362880)*n^3 + (13912639/1663200)*n^2 + (21001/3465)*n - 6