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A135434 a(n) is the smallest odd number that makes a(n)*2^N(n)-1 prime, where N(n) is the n-th Mersenne number that makes 2^N(n)-1 prime. 2
3, 3, 7, 3, 9, 7, 51, 15, 69, 19, 25, 103, 1905, 273, 139, 13, 4027, 3619, 2187, 3211, 6621, 1897, 17461, 2511, 90579, 30189, 805, 86539, 30091, 317917, 198681, 755061, 1283911, 26869, 1564347, 4348099, 383731, 6020095 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
First 22 terms are obtained by Mathematica. Terms from 23 to 38 are obtained by Jean Penna's LLR program.
LINKS
Jean Penna, LLR.
Lei Zhou, Prime page
EXAMPLE
First Mersenne number N(1)=2, 2^2-1=3 is the first Mersenne prime. 3*2^2-1=11 is prime;
Fifth Mersenne number N(5)=13, 2^13-1=8191 is the fifth Mersenne prime. 9*2^13-1=73727 is prime.
CROSSREFS
Cf. A000043.
Sequence in context: A182139 A092693 A134661 * A204204 A164928 A253249
KEYWORD
nonn,hard,more
AUTHOR
Lei Zhou, Dec 13 2007
EXTENSIONS
a(35)-a(37) from Pierre CAMI, Apr 06 2015
a(38) from Lei Zhou, Sep 04 2022
STATUS
approved

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Last modified June 16 02:19 EDT 2024. Contains 373416 sequences. (Running on oeis4.)