

A079324


k such that 2kp+1 is the first factor of a nonprime Mersenne number M(p) = 2^p  1.


2



1, 1, 4, 3, 163, 5, 25, 60, 1525, 1445580, 1609, 3, 17, 1, 59, 36793758459, 12379533, 3421967, 15, 1, 116905896337578232, 20236572837, 290792847537859675, 60, 2713800, 461, 7033, 2112, 1, 120, 1, 35807, 19, 413328944, 36, 41
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OFFSET

1,3


COMMENTS

a(188) = 216 = k = (f1)/2p for p=1231, f=531793. Although Mersenne numbers with p = 1213, 1217, 1229, 1231 are not fully factored, we know their smallest factors. One factor is known for p=1237 but it is not certain that it is the smallest.  Gord Palameta, Sep 26 2018


LINKS

Gord Palameta, Table of n, a(n) for n = 1..188


EXAMPLE

2^11  1 = 23*89, 23 = 2*1*11 + 1, therefore a(1) = 1.


PROG

(PARI) forprime (n=3, 101, v=2^n1; if (!isprime(v), print1((factor(v)[, 1][1]1)\(2*n)", ")))


CROSSREFS

Cf. A054723.
Sequence in context: A300026 A266255 A325871 * A002298 A195565 A335913
Adjacent sequences: A079321 A079322 A079323 * A079325 A079326 A079327


KEYWORD

nonn


AUTHOR

Jon Perry, Feb 12 2003


EXTENSIONS

More terms from Michel Marcus, Mar 17 2014


STATUS

approved



