Number of n X 3 binary arrays with rows and columns in nondecreasing order.

Terms

a(0) =4a(1) =14a(2) =45a(3) =130a(4) =336a(5) =785a(6) =1682a(7) =3351a(8) =6280a(9) =11176a(10) =19031a(11) =31200a(12) =49492a(13) =76275a(14) =114596a(15) =168317a(16) =242268a(17) =342418a(18) =476065a(19) =652046a(20) =880968a(21) =1175461a(22) =1550454a(23) =2023475a(24) =2614976a(25) =3348684a(26) =4251979a(27) =5356300a(28) =6697580a(29) =8316711