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A058663
a(n) = gcd(n-1, n-phi(n)).
2
0, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 7, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 23, 1, 1, 1, 1, 1, 5, 1, 1, 1, 1, 1, 3, 1, 1, 21, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1
OFFSET
1,10
LINKS
FORMULA
a(n) = gcd(n-1, cototient(n)) = gcd(n-1, A051953(n)).
EXAMPLE
For n = 15; n-1 = 14, cototient(15) = 15-phi(15) = 7, a(15) = gcd(14,7) = 7; For most n-s, among others for primes a(n) = 1.
MAPLE
with(numtheory); A058663:=n->igcd(n-1, n-phi(n)); seq(A058663(n), n=1..100); # Wesley Ivan Hurt, Apr 01 2014
MATHEMATICA
Table[GCD[n - 1, n - EulerPhi[n]], {n, 100}] (* Wesley Ivan Hurt, Apr 01 2014 *)
PROG
(PARI) A058663(n) = gcd(n-1, n-eulerphi(n)); \\ Antti Karttunen, Sep 25 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Dec 28 2000
STATUS
approved