A058515 - OEIS

%I #18 Aug 23 2017 06:00:53

%S 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,

%T 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,

%U 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

%N GCD of totients of consecutive integers.

%H Antti Karttunen, <a href="/A058515/b058515.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = gcd(Phi(n+1), Phi(n)), where Phi = A000010.

%e n=61, gcd(Phi(62), Phi(61)) = gcd(30, 60) = 30, so a(61)=30.

%t Map[GCD @@ # &, Partition[EulerPhi@ Range@ 98, 2, 1]] (* _Michael De Vlieger_, Aug 22 2017 *)

%o (PARI) a(n) = gcd(eulerphi(n), eulerphi(n+1)); \\ _Michel Marcus_, Dec 10 2013

%Y Cf. A000010, A049586, A060778.

%K nonn

%O 1,3

%A _Labos Elemer_, Dec 21 2000

%E Offset corrected to 1 by _Michel Marcus_, Dec 10 2013