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 A340078 a(n) = gcd(n, 1+A018804(n)), where A018804(n) = Sum_{k=1..n} gcd(k, n). 3

%I

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

%H Antti Karttunen, <a href="/A340078/b340078.txt">Table of n, a(n) for n = 1..8191</a>

%H Antti Karttunen, <a href="/A340078/a340078.txt">Data supplement: n, a(n) computed for n = 1..65537</a>

%F a(n) = gcd(n, 1+A018804(n)).

%o (PARI)

%o A018804(n) = sumdiv(n, d, n*eulerphi(d)/d); \\ From A018804

%o A340078(n) = gcd(n,1+A018804(n));

%Y Cf. A018804, A340079, A340080.

%Y Cf. also A055023, A323071 (similar but different sequences).

%K nonn

%O 1,2

%A _Antti Karttunen_, Dec 30 2020

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Last modified September 20 03:47 EDT 2021. Contains 347577 sequences. (Running on oeis4.)