A318668 a(n) = gcd(n, A064988(n)).

1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 5, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 15, 1, 1, 1, 1, 1, 9, 1, 1, 1, 1, 1, 3, 1, 1, 5, 1, 1, 3, 1, 1, 1, 1, 1, 3, 11, 1, 1, 1, 1, 15, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 9, 1, 1, 5, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 15, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 5

Offset

1,6

Comments

a(n) > 1 if and only if the prime factorization of n contains at least two distinct primes, p and q, such that q = prime(p).

Links

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

Index entries for sequences computed from indices in prime factorization

Formula

a(n) = gcd(n, A064988(n)).

Prog

(PARI) A318668(n) = { my(f = factor(n)); for (k=1, #f~, f[k, 1] = prime(f[k, 1]); ); gcd(n, factorback(f)); }; \\ After code in A064988.

Crossrefs

Cf. A064988, A318660.

Sequence in context: A214071 A226915 A180173 * A322361 A219208 A336850

Adjacent sequences: A318665 A318666 A318667 * A318669 A318670 A318671

Keyword

nonn

Author

Antti Karttunen, Sep 11 2018

Status

approved