a(n) = (prime(n)-3)*(prime(n)-5)/8.

Terms

a(0) =0a(1) =0a(2) =1a(3) =6a(4) =10a(5) =21a(6) =28a(7) =45a(8) =78a(9) =91a(10) =136a(11) =171a(12) =190a(13) =231a(14) =300a(15) =378a(16) =406a(17) =496a(18) =561a(19) =595a(20) =703a(21) =780a(22) =903a(23) =1081a(24) =1176a(25) =1225a(26) =1326a(27) =1378a(28) =1485a(29) =1891