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A110337
a(n) = 2n+1 if 2n+1 is prime else a(n) = least prime of the form (2n+1)(2n+3)...(2n+2k-1) + 2.
0
3, 5, 7, 101, 11, 13, 257, 17, 19, 9454727, 23, 677, 801011, 29, 31, 42737, 1297, 37, 1601, 41, 43, 5285387, 47, 410006013351009077, 148667, 53, 3137, 56284059197, 59, 61, 1529270318745462748663049625086428127, 4357, 67, 26822027, 71, 73
OFFSET
1,1
EXAMPLE
a(4) = 9*11+2= 101, as 9 is composite.
PROG
(PARI) a(n) = {pr = 2*n+1; if (isprime(pr), return (pr)); pa = pr; ok = 0; while (! ok, pa += 2; pr *= pa; ok = isprime(pr + 2); ); pr + 2; } \\ Michel Marcus, Sep 16 2013
CROSSREFS
Cf. A110336.
Sequence in context: A051345 A242387 A104388 * A132287 A046201 A374101
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Jul 20 2005
EXTENSIONS
More terms from Victoria Sapko (vsapko(AT)frc.mass.edu), Sep 28 2007
Corrected and extended by Michel Marcus, Sep 16 2013
STATUS
approved