a(n) = gcd(n, d(n)), where d(n) is the number of divisors of n (A000005).

Terms

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