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A139257
Twice Mersenne primes A000668(n).
7
6, 14, 62, 254, 16382, 262142, 1048574, 4294967294, 4611686018427387902, 1237940039285380274899124222, 324518553658426726783156020576254, 340282366920938463463374607431768211454
OFFSET
1,1
COMMENTS
Radicals of even perfect numbers. - Charles R Greathouse IV, Feb 01 2013
LINKS
Florian Luca and Carl Pomerance, On the radical of a perfect number, New York Journal of Math., 16 (2010), 23-30; alternative link.
FORMULA
a(n) = 2*A000668(n).
a(n) = A000918(1 + A000043(n)) = A095121(A000043(n)). - Omar E. Pol, Jun 07 2012
MATHEMATICA
2*(2^MersennePrimeExponent[Range[15]]-1) (* Harvey P. Dale, Jan 05 2020 *)
PROG
(PARI) apply(p->2*(2^p-1), select(p->ispseudoprime(2^p-1), primes(40))) \\ Charles R Greathouse IV, Feb 01 2013
KEYWORD
nonn
AUTHOR
Omar E. Pol, Apr 23 2008
EXTENSIONS
Corrected and extended by Joerg Arndt, Jun 07 2012.
STATUS
approved