|
| |
|
|
A090748
|
|
Numbers n such that 2^(n+1) - 1 is prime.
|
|
18
| |
|
|
1, 2, 4, 6, 12, 16, 18, 30, 60, 88, 106, 126, 520, 606, 1278, 2202, 2280, 3216, 4252, 4422, 9688, 9940, 11212, 19936, 21700, 23208, 44496, 86242, 110502, 132048, 216090, 756838, 859432, 1257786, 1398268, 2976220, 3021376, 6972592, 13466916
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
COMMENTS
| Perfect numbers A000396(n) = 2^A133033(n) - 2^a(n), assuming there are no odd perfect numbers. - Omar E. Pol (info(AT)polprimos.com), Feb 24 2008
Number of proper divisors of n-th even perfect number that are multiples of n-th Mersenne prime A000668(n). - Omar E. Pol (info(AT)polprimos.com), Feb 28 2008
Base 2 logarithm of n-th even superperfect number A061652(n). Also base 2 logarithm of n-th superperfect number A019279(n), assuming there are no odd superperfect numbers. - Omar E. Pol (info(AT)polprimos.com), Apr 11 2008
Number of 0's in binary expansion of n-th even perfect number (see A135650). - Omar E. Pol (info(AT)polprimos.com), May 04 2008
|
|
|
LINKS
| O. E. Pol, Determinacion geometrica de los numeros primos y perfectos.
|
|
|
EXAMPLE
| a(1) = 1 because 2^2 - 1 = 3 is prime
|
|
|
MATHEMATICA
| lst={}; Do[If[PrimeQ[2^(n+1)-1], AppendTo[lst, n]], {n, 10^5}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Aug 21 2008]
|
|
|
CROSSREFS
| a(n) = A000043(n) - 1. A000043 is the main entry for this sequence.
Cf. A000396, A133033, A000668.
Cf. A019279, A061652.
Cf. A135650.
Sequence in context: A141113 A050584 A019280 * A188047 A032465 A089395
Adjacent sequences: A090745 A090746 A090747 * A090749 A090750 A090751
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Feb 03 2004
|
|
|
EXTENSIONS
| Edited, corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 09 2004
Updated (a(39)) by Omar E. Pol (info(AT)polprimos.com), Jan 23 2009
|
| |
|
|
