A171263 - OEIS

%I #10 Mar 19 2018 06:43:35

%S 30241,2178541,23569921,66433720321,630532357710420079508428362350593,

%T 1928622300236318049928258133164033,

%U 651350717502447739281012140234441171379683329

%N Primes of the form 1 + 4-multiperfect numbers.

%C A subsequence of A093034. If p is a term of this sequence then for each positive integer k, x=p^k is a solution for the equation sigma(phi(x))=4(x-1). See comment lines of the sequence A093034.

%e p=30241 is prime and sigma(p-1)/(p-1)=4, so p is in the sequence.

%Y Cf. A027687, A093034, A171264, A171265.

%K fini,full,nonn

%O 1,1

%A _M. F. Hasler_ and _Farideh Firoozbakht_, Apr 15 2010