Truncated triangular pyramid numbers: a(n) = (n-7)*(n^2 + 10*n - 108)/6, n >= 8.

Terms

a(0) =6a(1) =21a(2) =46a(3) =82a(4) =130a(5) =191a(6) =266a(7) =356a(8) =462a(9) =585a(10) =726a(11) =886a(12) =1066a(13) =1267a(14) =1490a(15) =1736a(16) =2006a(17) =2301a(18) =2622a(19) =2970a(20) =3346a(21) =3751a(22) =4186a(23) =4652a(24) =5150a(25) =5681a(26) =6246a(27) =6846a(28) =7482a(29) =8155