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

1,1

Comments

Row 3 of A224374

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

Example

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

Crossrefs

Sequence in context: A231911 A182130 A224311 * A010832 A022719 A290405

Adjacent sequences: A224372 A224373 A224374 * A224376 A224377 A224378

Keyword

nonn

Author

R. H. Hardin Apr 05 2013

Status

approved