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a(n) is the smallest integer k for which sigma_n(k) <= sigma_n(k-1) where sigma_n(k) = sum of the n-th powers of the divisors of k.
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%I #6 Aug 18 2013 03:24:28

%S 3,5,7,25,61,145,361,853,1969,4489,10069,22273,48781,105949,228589,

%T 490405,1046977,2225965,4715401,9956977,20965213,44031361,92262349,

%U 192920785,402629257,838827577,1744784389,3623814865,7516104565

%N a(n) is the smallest integer k for which sigma_n(k) <= sigma_n(k-1) where sigma_n(k) = sum of the n-th powers of the divisors of k.

%C a(n) has to be larger than the solution to Zeta(n)*(x-1)^n=x^n.

%e a(1)=5 since sigma(1)=1,sigma(2)=3,sigma(3)=4, sigma(4)=7, but sigma(5)=6.

%o (PARI) a(n) = {my(k = 2); while(sigma(k, n) > sigma(k-1, n), k++); k;} \\ _Michel Marcus_, Aug 18 2013

%K nonn

%O 0,1

%A _John L. Drost_, Oct 26 2004