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 A139257 Twice Mersenne primes A000668(n). 5
 6, 14, 62, 254, 16382, 262142, 1048574, 4294967294, 4611686018427387902, 1237940039285380274899124222, 324518553658426726783156020576254, 340282366920938463463374607431768211454 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Radicals of even perfect numbers. - Charles R Greathouse IV, Feb 01 2013 LINKS F. Luca and C. Pomerance, On the radical of a perfect number, New York Journal of Math., 16 (2010), 23-30. FORMULA a(n) = 2*A000668(n). a(n) = A000918(1 + A000043(n)) = A095121(A000043(n)).  - Omar E. Pol, Jun 07 2012 PROG (PARI) apply(p->2*(2^p-1), select(p->ispseudoprime(2^p-1), primes(40))) \\ Charles R Greathouse IV, Feb 01 2013 CROSSREFS Cf. A000043, A000668, A000918, A060590, A095121, A100484, A139256. Sequence in context: A032404 A059954 A252541 * A056842 A182752 A200033 Adjacent sequences:  A139254 A139255 A139256 * A139258 A139259 A139260 KEYWORD nonn AUTHOR Omar E. Pol, Apr 23 2008 EXTENSIONS Corrected and extended by Joerg Arndt, Jun 07 2012. STATUS approved

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Last modified December 9 15:04 EST 2019. Contains 329877 sequences. (Running on oeis4.)