a(n) = 1 - sigma(n) + sigma(n)^2.

Terms

a(0) =1a(1) =7a(2) =13a(3) =43a(4) =31a(5) =133a(6) =57a(7) =211a(8) =157a(9) =307a(10) =133a(11) =757a(12) =183a(13) =553a(14) =553a(15) =931a(16) =307a(17) =1483a(18) =381a(19) =1723a(20) =993a(21) =1261a(22) =553a(23) =3541a(24) =931a(25) =1723a(26) =1561a(27) =3081a(28) =871a(29) =5113