A171263 Primes of the form 1 + 4-multiperfect numbers.

30241, 2178541, 23569921, 66433720321, 630532357710420079508428362350593, 1928622300236318049928258133164033, 651350717502447739281012140234441171379683329

Offset: 1

Author

M. F. Hasler and Farideh Firoozbakht, Apr 15 2010

Keywords

• fini
• full
• nonn

Comments

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.

Examples

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

Crossrefs

Cf. A027687, A093034, A171264, A171265.