a(n) = (n-1)*(n-2)*(n-3) + n.

Terms

a(0) =1a(1) =2a(2) =3a(3) =10a(4) =29a(5) =66a(6) =127a(7) =218a(8) =345a(9) =514a(10) =731a(11) =1002a(12) =1333a(13) =1730a(14) =2199a(15) =2746a(16) =3377a(17) =4098a(18) =4915a(19) =5834a(20) =6861a(21) =8002a(22) =9263a(23) =10650a(24) =12169a(25) =13826a(26) =15627a(27) =17578a(28) =19685a(29) =21954