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%I #2 Mar 30 2012 17:27:47
%S 1,8,20,48,144,240,720,480,756,720,864,2304,2880,4080,5040,6240,6048,
%T 6720,9984,21600,90720,506880,806400,748800,973440,1153152
%N a(n) = sigma(A067651(n)).
%C Numbers n such that n = sigma(k) = phi(prime(k)-1) for some k.
%C Values of k are in A067651, values of prime(k) are in A107815.
%e a(3) = sigma(A067651(3)) = sigma(19) = 20.
%o (PARI) m=400000;for(n=1,m,s=sigma(n);if(s==eulerphi(prime(n)-1),print1(s,",")))
%Y Cf. A067651, A107815.
%K nonn,more
%O 1,2
%A _Klaus Brockhaus_, May 24 2005
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