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%I A084217 #14 Jan 19 2025 11:47:40
%S A084217 1,1,1,1,2,1,2,1,1,1,2,1,2,2,2,1,2,1,2,1,1,2,2,1,3,2,1,2,2,1,2,1,2,2,
%T A084217 4,1,2,2,2,1,2,1,2,2,2,2,2,1,3,1,2,3,2,1,2,2,2,2,2,1,2,2,1,1,4,2,2,2,
%U A084217 2,3,2,1,2,2,3,2,4,1,2,2,1,2,2,1,4,2,2,3,2,1,4,2,2,2,5,1,2,3,2,1,2,2,2,2,2
%N A084217 Number of k's 1<=k<=n dividing the numerator of 2n-th Bernoulli number.
%H A084217 Antti Karttunen, <a href="/A084217/b084217.txt">Table of n, a(n) for n = 1..5530</a>
%H A084217 Wikipedia, <a href="https://en.wikipedia.org/wiki/Bernoulli_number">Bernoulli numbers</a>
%o A084217 (PARI) a(n)=sum(k=1,n,if(numerator(bernfrac(2*n))%k,0,1))
%Y A084217 Cf. A000367.
%K A084217 nonn,changed
%O A084217 1,5
%A A084217 _Benoit Cloitre_, Jun 21 2003
%E A084217 Missing a(1)=1 inserted and data section extended to a(105) by _Antti Karttunen_, Jan 19 2025

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