(p*q - 1)/2 where p and q are consecutive odd primes.

Terms

a(0) =7a(1) =17a(2) =38a(3) =71a(4) =110a(5) =161a(6) =218a(7) =333a(8) =449a(9) =573a(10) =758a(11) =881a(12) =1010a(13) =1245a(14) =1563a(15) =1799a(16) =2043a(17) =2378a(18) =2591a(19) =2883a(20) =3278a(21) =3693a(22) =4316a(23) =4898a(24) =5201a(25) =5510a(26) =5831a(27) =6158a(28) =7175a(29) =8318