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A050921
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Smallest prime of form n*2^m+1, m >= 0, or 0 if no prime exists.
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12
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2, 3, 7, 5, 11, 7, 29, 17, 19, 11, 23, 13, 53, 29, 31, 17, 137, 19, 1217, 41, 43, 23, 47, 97, 101, 53, 109, 29, 59, 31, 7937, 257, 67, 137, 71, 37, 149, 1217, 79, 41, 83, 43, 173, 89, 181, 47
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OFFSET
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1,1
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COMMENTS
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Primes arising from A040076 (or 0 if no such prime exists).
Or: Starting with x=n+1, the first prime created by iterating the map x-> 2*x-1. - Kevin L. Schwartz and Christian N. K. Anderson, May 13 2013
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LINKS
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R. J. Mathar, Table of n, a(n) for n = 1..382
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MAPLE
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A050921 := proc(n)
for m from 0 do
if isprime(n*2^m+1) then
return n*2^m+1 ;
end if;
end do;
end proc; # R. J. Mathar, Jun 01 2013
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MATHEMATICA
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Do[m = 0; While[ !PrimeQ[n*2^m + 1], m++ ]; Print[n*2^m + 1], {n, 1, 47} ]
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CROSSREFS
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Cf. A040076, A034694, A038699.
Sequence in context: A241082 A219789 A034694 * A087386 A110359 A092977
Adjacent sequences: A050918 A050919 A050920 * A050922 A050923 A050924
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KEYWORD
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nonn,easy,nice
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AUTHOR
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N. J. A. Sloane, Dec 30 1999
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EXTENSIONS
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The next term (47*2^583 + 1) is too large to show.
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STATUS
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approved
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