a(n) = primefloor(n)*primeceiling(n) - previousprime(n)*nextprime(n).

Terms

a(0) =-1a(1) =0a(2) =4a(3) =0a(4) =-6a(5) =0a(6) =0a(7) =0a(8) =30a(9) =0a(10) =-18a(11) =0a(12) =0a(13) =0a(14) =42a(15) =0a(16) =-30a(17) =0a(18) =0a(19) =0a(20) =-22a(21) =0a(22) =0a(23) =0a(24) =0a(25) =0a(26) =128a(27) =0a(28) =-112a(29) =0