a(n) = 3*2*1 + 6*5*4 + 9*8*7 + 12*11*10 + ... + (up to the n-th term).

Terms

a(0) =3a(1) =6a(2) =6a(3) =12a(4) =36a(5) =126a(6) =135a(7) =198a(8) =630a(9) =642a(10) =762a(11) =1950a(12) =1965a(13) =2160a(14) =4680a(15) =4698a(16) =4986a(17) =9576a(18) =9597a(19) =9996a(20) =17556a(21) =17580a(22) =18108a(23) =29700a(24) =29727a(25) =30402a(26) =47250a(27) =47280a(28) =48120a(29) =71610