(prime(n)-1)(prime(n)-3)/8.

Terms

a(0) =0a(1) =1a(2) =3a(3) =10a(4) =15a(5) =28a(6) =36a(7) =55a(8) =91a(9) =105a(10) =153a(11) =190a(12) =210a(13) =253a(14) =325a(15) =406a(16) =435a(17) =528a(18) =595a(19) =630a(20) =741a(21) =820a(22) =946a(23) =1128a(24) =1225a(25) =1275a(26) =1378a(27) =1431a(28) =1540a(29) =1953