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
Keywords
Examples
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
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
Comments