A353643 The greatest common divisor of phi(n) and phi(sigma(n)).

1, 1, 2, 2, 2, 2, 2, 4, 6, 2, 2, 4, 6, 2, 8, 2, 2, 6, 2, 4, 4, 2, 2, 8, 10, 12, 2, 12, 4, 8, 2, 4, 4, 2, 8, 12, 18, 2, 24, 8, 4, 4, 2, 4, 24, 2, 2, 4, 6, 20, 8, 6, 2, 2, 8, 8, 4, 4, 2, 16, 30, 2, 12, 2, 24, 4, 2, 4, 4, 24, 2, 24, 36, 36, 20, 12, 4, 24, 2, 4, 2, 4, 2, 24, 4, 2, 8, 8, 8, 24, 24, 4, 4, 2, 8, 8, 6, 6

Offset

1,3

Links

Antti Karttunen, Table of n, a(n) for n = 1..16384

Antti Karttunen, Data supplement: n, a(n) computed for n = 1..65537

Index entries for sequences related to sigma(n)

Formula

a(n) = gcd(A000010(n), A062401(n)).

a(n) = gcd(A000010(n), A353636(n)) = gcd(A062401(n), A353636(n)).

a(n) = A000010(n) / A353644(n).

a(n) = A062401(n) / A353646(n).

Mathematica

a[n_] := GCD[EulerPhi[n], EulerPhi[DivisorSigma[1, n]]]; Array[a, 100] (* Amiram Eldar, May 06 2022 *)

Prog

(PARI) A353643(n) = gcd(eulerphi(sigma(n)), eulerphi(n));

Crossrefs

Cf. A000010, A000203, A062401, A353636, A353644, A353646.

Sequence in context: A029103 A175732 A327817 * A168260 A008737 A244460

Adjacent sequences: A353640 A353641 A353642 * A353644 A353645 A353646

Keyword

nonn

Author

Antti Karttunen, May 06 2022

Status

approved