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
KEYWORD
nonn
AUTHOR
Labos Elemer, Dec 21 2000
EXTENSIONS
Offset corrected to 1 by Michel Marcus, Dec 10 2013
STATUS
approved