a(n) = n^2 - primefloor(n)*primeceiling(n).

Terms

a(0) =0a(1) =0a(2) =1a(3) =0a(4) =1a(5) =0a(6) =-13a(7) =4a(8) =23a(9) =0a(10) =1a(11) =0a(12) =-25a(13) =4a(14) =35a(15) =0a(16) =1a(17) =0a(18) =-37a(19) =4a(20) =47a(21) =0a(22) =-91a(23) =-42a(24) =9a(25) =62a(26) =117a(27) =0a(28) =1a(29) =0