

A058515


GCD of totients of consecutive integers.


10



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
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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.


EXAMPLE

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.
Sequence in context: A237975 A327343 A032574 * A126696 A244464 A250201
Adjacent sequences: A058512 A058513 A058514 * A058516 A058517 A058518


KEYWORD

nonn


AUTHOR

Labos Elemer, Dec 21 2000


EXTENSIONS

Offset corrected to 1 by Michel Marcus, Dec 10 2013


STATUS

approved



