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%I #6 Nov 14 2019 12:14:29
%S 673,523777
%N Primes of the form 1 + triperfect numbers.
%C A subsequence of A093034.
%C If p is a term of this sequence then for each positive integer k, x=p^k
%C is a solution for the equation sigma(phi(x))=3(x-1). See comment lines of
%C the sequence A093034.
%H Achim Flammenkamp, <a href="http://wwwhomes.uni-bielefeld.de/achim/mpn.html">The Multiply Perfect Numbers Page</a>
%e p=673 is prime and sigma(p-1)/(p-1)=3, so p is in the sequence.
%Y Cf. A005820, A093034, A171263, A171264, A171265.
%K fini,full,nonn,bref
%O 1,1
%A _M. F. Hasler_ and _Farideh Firoozbakht_, Apr 15 2010
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