A303781 a(2) = 1; for n <> 2, a(n) = gcd(n, A000005(n)), where A000005(n) = number of divisors of n.

1, 1, 1, 1, 1, 2, 1, 4, 3, 2, 1, 6, 1, 2, 1, 1, 1, 6, 1, 2, 1, 2, 1, 8, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 9, 1, 2, 1, 8, 1, 2, 1, 2, 3, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 8, 1, 2, 1, 12, 1, 2, 3, 1, 1, 2, 1, 2, 1, 2, 1, 12, 1, 2, 3, 2, 1, 2, 1, 10, 1, 2, 1, 12, 1, 2, 1, 8, 1, 6, 1, 2, 1, 2, 1, 12, 1, 2, 3, 1, 1, 2, 1, 8, 1

Offset

1,6

Comments

Except for a(2) = 1, a(n) = A009191(n).

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Formula

a(2) = 1; for n <> 2, a(n) = gcd(n, A000005(n)).

Mathematica

Join[{1, 1}, Table[GCD[n, DivisorSigma[0, n]], {n, 3, 110}]] (* Harvey P. Dale, Mar 20 2023 *)

Prog

(PARI) A303781(n) = if(2==n, 1, gcd(n, numdiv(n)));

Crossrefs

Cf. A000005, A009191.

Sequence in context: A300823 A345942 A175702 * A216377 A253515 A319521

Adjacent sequences: A303778 A303779 A303780 * A303782 A303783 A303784

Keyword

nonn

Author

Antti Karttunen, Apr 30 2018

Status

approved