cp's OEIS Frontend

A340078 a(n) = gcd(n, 1+A018804(n)), where A018804(n) = Sum_{k=1..n} gcd(k, n).

%I A340078 #6 Dec 31 2020 08:20:31
%S A340078 1,2,3,1,5,2,7,1,1,2,11,1,13,2,1,1,17,2,19,1,3,2,23,1,1,2,1,7,29,2,31,
%T A340078 1,1,2,1,1,37,2,3,1,41,14,43,1,5,2,47,1,1,2,1,1,53,2,5,1,3,2,59,1,61,
%U A340078 2,1,1,1,2,67,1,1,2,71,1,73,2,1,1,1,2,79,1,1,2,83,1,1,2,1,1,89,2,1,1,3,2,1,3,97,2
%N A340078 a(n) = gcd(n, 1+A018804(n)), where A018804(n) = Sum_{k=1..n} gcd(k, n).
%H A340078 Antti Karttunen, <a href="/A340078/b340078.txt">Table of n, a(n) for n = 1..8191</a>
%H A340078 Antti Karttunen, <a href="/A340078/a340078.txt">Data supplement: n, a(n) computed for n = 1..65537</a>
%F A340078 a(n) = gcd(n, 1+A018804(n)).
%o A340078 (PARI)
%o A340078 A018804(n) = sumdiv(n, d, n*eulerphi(d)/d); \\ From A018804
%o A340078 A340078(n) = gcd(n,1+A018804(n));
%Y A340078 Cf. A018804, A340079, A340080.
%Y A340078 Cf. also A055023, A323071 (similar but different sequences).
%K A340078 nonn
%O A340078 1,2
%A A340078 _Antti Karttunen_, Dec 30 2020