A223988 Number of 3Xn 0..3 arrays with rows unimodal and columns nondecreasing

20, 400, 5029, 44803, 308470, 1738756, 8350154, 35158856, 132595894, 455284536, 1441678804, 4253578398, 11791889562, 30929283640, 77204065141, 184304047745, 422556706314, 933834642586, 1995549087157, 4134881948947, 8327774224280

Offset

1,1

Comments

Row 3 of A223987

Links

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

Formula

Empirical: a(n) = (1/3629463552000)*n^18 + (1/44808192000)*n^17 + (10403/10461394944000)*n^16 + (10537/373621248000)*n^15 + (2915977/5230697472000)*n^14 + (6071381/747242496000)*n^13 + (748919/8211456000)*n^12 + (23111713/28740096000)*n^11 + (409218107/73156608000)*n^10 + (320706361/10450944000)*n^9 + (107018740483/804722688000)*n^8 + (467745209/1026432000)*n^7 + (10942630223/8895744000)*n^6 + (239853259979/93405312000)*n^5 + (882554800469/217945728000)*n^4 + (6093492161/1297296000)*n^3 + (4200944633/1029188160)*n^2 + (1784593/1021020)*n + 1

Example

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

Crossrefs

Sequence in context: A188759 A223866 A207091 * A189698 A209433 A188988

Adjacent sequences: A223985 A223986 A223987 * A223989 A223990 A223991

Keyword

nonn

Author

R. H. Hardin Mar 30 2013

Status

approved