a(n) = gcd(d(n), sigma(n)).

Terms

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