Number of n X 2 0..2 arrays with rows and columns in nondecreasing order.

Terms

a(0) =6a(1) =29a(2) =112a(3) =356a(4) =972a(5) =2359a(6) =5217a(7) =10704a(8) =20647a(9) =37818a(10) =66287a(11) =111865a(12) =182651a(13) =289698a(14) =447814a(15) =676515a(16) =1001148a(17) =1454203a(18) =2076834a(19) =2920610a(20) =4049518a(21) =5542241a(22) =7494735a(23) =10023130a(24) =13266981a(25) =17392896a(26) =22598569a(27) =29117247a(28) =37222661a(29) =47234452