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A057026
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Smallest prime of form (2n+1)*2^m-1 for some m, or 0 if no such prime exists.
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4
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3, 2, 19, 13, 17, 43, 103, 29, 67, 37, 41, 367, 199, 53, 463, 61, 131, 139, 73, 311, 163, 5503, 89, 751, 97, 101, 211, 109, 113, 241663, 487, 251, 1039, 2143, 137, 283, 9343, 149, 307, 157, 647, 331, 2719, 173, 1423, 181, 743, 379, 193, 197, 103423, 823, 419
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OFFSET
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0,1
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COMMENTS
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If a(329) > 0 it is greater than 659*2^10000. - Robert Israel, Jul 01 2014
Indeed, a(329) > 659*2^100000 if it is nonzero. There does not appear to be a covering set, though, so probably a(329) > 0. - Charles R Greathouse IV, Jul 02 2014
a(329) = 659*2^800516 - 1 (found by David W Linton in 2004). - Robert Israel, Jul 04 2014
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LINKS
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Robert Israel, Table of n, a(n) for n = 0..328
Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime
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EXAMPLE
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a(5)=43 because 2*5+1=11 and smallest prime of the form 11*2^m-1 is 43 (since 10 and 21 are not prime)
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MAPLE
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A057026:= proc(n)
local t;
t:= 2*n;
while not isprime(t) do t:= 2*t+1 od;
t
end proc;
seq(A057026(n), n=0..328); # Robert Israel, Jul 01 2014
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CROSSREFS
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Cf. A057024, A057025, A038699.
Sequence in context: A078073 A317927 A075568 * A032448 A066195 A090587
Adjacent sequences: A057023 A057024 A057025 * A057027 A057028 A057029
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KEYWORD
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nonn
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AUTHOR
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Henry Bottomley, Jul 24 2000
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STATUS
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approved
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