A062754 - OEIS

%I #14 Dec 16 2017 22:41:18

%S 1,2,1,2,1,2,1,1,9,2,1,2,1,2,1,2,1,2,1,4,3,2,1,1,1,2,1,2,1,2,1,16,3,2,

%T 7,2,1,2,3,2,1,2,1,2,9,2,1,3,1,2,1,2,1,18,5,8,3,2,1,2,1,2,1,4,1,2,1,4,

%U 3,2,1,2,1,2,5,4,7,2,1,1,9,2,1,12,1,2,3,2,1,2,7,4,3,2,1,2,1,2,1,2,1,2

%N a(n) = gcd(n, sigma(n+1)).

%H Antti Karttunen, <a href="/A062754/b062754.txt">Table of n, a(n) for n = 1..16384</a>

%t Table[GCD[n,DivisorSigma[1,n+1]],{n,110}] (* _Harvey P. Dale_, May 25 2015 *)

%o (PARI) j=[]; for(n=1,200,j=concat(j,gcd(n, sigma(n+1)))); j

%o (PARI) a(n) = gcd(n, sigma(n+1)); \\ _Michel Marcus_, Dec 16 2017

%Y Cf. A000203, A009194.

%K nonn

%O 1,2

%A _Jason Earls_, Jul 15 2001