a(n) = (prime(n)^2 - 1)/8.

Terms

a(0) =1a(1) =3a(2) =6a(3) =15a(4) =21a(5) =36a(6) =45a(7) =66a(8) =105a(9) =120a(10) =171a(11) =210a(12) =231a(13) =276a(14) =351a(15) =435a(16) =465a(17) =561a(18) =630a(19) =666a(20) =780a(21) =861a(22) =990a(23) =1176a(24) =1275a(25) =1326a(26) =1431a(27) =1485a(28) =1596a(29) =2016