a(n) = (prime(n)^2 - prime(n-1)*prime(n+1))/2, n >= 3.

Terms

a(0) =2a(1) =-3a(2) =15a(3) =-9a(4) =21a(5) =-15a(6) =-11a(7) =64a(8) =-56a(9) =49a(10) =45a(11) =-39a(12) =-35a(13) =18a(14) =124a(15) =-116a(16) =79a(17) =75a(18) =-140a(19) =91a(20) =-71a(21) =-65a(22) =210a(23) =105a(24) =-99a(25) =111a(26) =-105a(27) =-537a(28) =663a(29) =-119