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A086669 a(n) = number of divisors of n that are fundamental discriminants. 4

%I

%S 1,1,1,1,2,1,1,2,1,2,1,2,2,1,2,2,2,1,1,2,2,1,1,4,2,2,1,2,2,2,1,2,2,2,

%T 2,2,2,1,2,4,2,2,1,2,2,1,1,4,1,2,2,2,2,1,2,4,2,2,1,4,2,1,2,2,4,2,1,2,

%U 2,2,1,4,2,2,2,2,2,2,1,4,1,2,1,4,4,1,2,4,2,2,2,2,2,1,2,4,2,1,2,2

%N a(n) = number of divisors of n that are fundamental discriminants.

%H Antti Karttunen, <a href="/A086669/b086669.txt">Table of n, a(n) for n = 1..16385</a>

%F a(n) = Sum_{d|n} A290098(d).

%e 10 has divisors 1, 2, 5 and 10 of which 1 and 5 are fundamental discriminants, so a(10)=2

%o (PARI) for (n=1,100,s=0; fordiv(i=n,i,s+=isfundamental(i)); print1(","s))

%o (PARI) A086669(n) = sumdiv(n, i, isfundamental(i)); \\ _Antti Karttunen_, Aug 22 2017

%Y Cf. A003658, A290098.

%K nonn

%O 1,5

%A _Jon Perry_, Jul 27 2003

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Last modified July 27 11:04 EDT 2021. Contains 346304 sequences. (Running on oeis4.)