a(n) = a(n-1) + n^2 if n prime else a(n-1) - n, starting with a(0) = 0.

Terms

a(0) =0a(1) =-1a(2) =3a(3) =12a(4) =8a(5) =33a(6) =27a(7) =76a(8) =68a(9) =59a(10) =49a(11) =170a(12) =158a(13) =327a(14) =313a(15) =298a(16) =282a(17) =571a(18) =553a(19) =914a(20) =894a(21) =873a(22) =851a(23) =1380a(24) =1356a(25) =1331a(26) =1305a(27) =1278a(28) =1250a(29) =2091