A058515 GCD of totients of consecutive integers.

1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 6, 2, 8, 8, 2, 6, 2, 4, 2, 2, 2, 4, 4, 6, 6, 4, 4, 2, 2, 4, 4, 8, 12, 12, 18, 6, 8, 8, 4, 6, 2, 4, 2, 2, 2, 2, 2, 4, 8, 4, 2, 2, 8, 12, 4, 2, 2, 4, 30, 6, 4, 16, 4, 2, 2, 4, 4, 2, 2, 24, 36, 4, 4, 12, 12, 6, 2, 2, 2, 2, 2, 8, 2, 14, 8, 8, 8, 24, 4, 4, 2, 2, 8, 32, 6

Offset

1,3

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Formula

a(n) = gcd(phi(n+1), phi(n)), where phi = A000010.

a(n) = A083542(n)/A066813(n). - Amiram Eldar, May 07 2025

Example

For n = 61, gcd(phi(62), phi(61)) = gcd(30, 60) = 30, so a(61) = 30.

Mathematica

Map[GCD @@ # &, Partition[EulerPhi@ Range@ 98, 2, 1]] (* Michael De Vlieger, Aug 22 2017 *)

Prog

(PARI) a(n) = gcd(eulerphi(n), eulerphi(n+1)); \\ Michel Marcus, Dec 10 2013

Crossrefs

Cf. A000010, A049586, A060778, A066813, A083542.

Sequence in context: A327343 A391788 A032574 * A126696 A244464 A250201

Adjacent sequences: A058512 A058513 A058514 * A058516 A058517 A058518

Keyword

nonn,easy

Author

Labos Elemer, Dec 21 2000

Extensions

Offset corrected to 1 by Michel Marcus, Dec 10 2013

Status

approved