Number of n X 3 0..3 arrays with rows unimodal and columns nondecreasing.

Terms

a(0) =50a(1) =684a(2) =5029a(3) =25410a(4) =99634a(5) =325120a(6) =922768a(7) =2346883a(8) =5462600a(9) =11818092a(10) =24045385a(11) =46430852a(12) =85704412a(13) =152105120a(14) =260790200a(15) =433664645a(16) =701719286a(17) =1107976716a(18) =1711156645a(19) =2590185158a(20) =3849685950a(21) =5626605920a(22) =8098142520a(23) =11491155975