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%I #16 Sep 14 2014 00:25:49
%S 2,7,29,673,30241,523777,2178541,23569921,33550337,66433720321,
%T 137438691329,30823866178561,796928461056001,1802582780370364661761,
%U 9186050031556349952001,2827987212986831882236723201
%N Primes of the form 1+multiple perfect numbers.
%C From _M. F. Hasler_ and _Farideh Firoozbakht_, Apr 08 2010: (Start)
%C Theorem: If p is a term of this sequence and p-1 is a t-perfect number then for each positive integer k, x=p^k is a solution to the equation sigma(phi(x)) = t*(x-1).
%C Proof: sigma(phi(x))=sigma(phi(p^k))=sigma((p-1)*p^(k-1))=sigma(p-1)*sigma(p^(k-1))=t*(p-1)*(p^k-1)/(p-1)=t*(p^k-1)=t*(x-1). (End)
%Y Cf. A007691.
%Y Cf. A171263, A171264, A171265. [From _M. F. Hasler_ and _Farideh Firoozbakht_, Apr 08 2010]
%K nonn
%O 1,1
%A _Labos Elemer_, May 12 2004
%E a(11)-a(16) from _Donovan Johnson_, Nov 30 2008
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