A139257 Twice Mersenne primes A000668(n).

6, 14, 62, 254, 16382, 262142, 1048574, 4294967294, 4611686018427387902, 1237940039285380274899124222, 324518553658426726783156020576254, 340282366920938463463374607431768211454

Offset: 1

Author

Omar E. Pol, Apr 23 2008

Keywords

• nonn

Comments

Radicals of even perfect numbers. - Charles R Greathouse IV, Feb 01 2013

Links

• Amiram Eldar, Table of n, a(n) for n = 1..18
• Florian Luca and Carl Pomerance, On the radical of a perfect number, New York Journal of Math., 16 (2010), 23-30; alternative link.

Crossrefs

Cf. A000043, A000668, A000918, A060590, A095121, A100484, A139256.

Programs

Mathematica

2*(2^MersennePrimeExponent[Range[15]]-1) (* Harvey P. Dale, Jan 05 2020 *)

PARI

apply(p->2*(2^p-1),select(p->ispseudoprime(2^p-1),primes(40))) \\ Charles R Greathouse IV, Feb 01 2013

Formula

a(n) = 2*A000668(n).

a(n) = A000918(1 + A000043(n)) = A095121(A000043(n)). - Omar E. Pol, Jun 07 2012

Extensions

Corrected and extended by Joerg Arndt, Jun 07 2012.