Truncated triangular pyramid numbers: a(n) = (n-5)*(n^2 + 8*n - 66)/6.

Terms

a(0) =3a(1) =13a(2) =31a(3) =58a(4) =95a(5) =143a(6) =203a(7) =276a(8) =363a(9) =465a(10) =583a(11) =718a(12) =871a(13) =1043a(14) =1235a(15) =1448a(16) =1683a(17) =1941a(18) =2223a(19) =2530a(20) =2863a(21) =3223a(22) =3611a(23) =4028a(24) =4475a(25) =4953a(26) =5463a(27) =6006a(28) =6583a(29) =7195