a(n) = prime(n)*(prime(n+1)-1)/2.

Terms

a(0) =2a(1) =6a(2) =15a(3) =35a(4) =66a(5) =104a(6) =153a(7) =209a(8) =322a(9) =435a(10) =558a(11) =740a(12) =861a(13) =989a(14) =1222a(15) =1537a(16) =1770a(17) =2013a(18) =2345a(19) =2556a(20) =2847a(21) =3239a(22) =3652a(23) =4272a(24) =4850a(25) =5151a(26) =5459a(27) =5778a(28) =6104a(29) =7119