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A111391
Numbers k such that 11*10^k - 1 is prime.
2
1, 9, 11, 17, 22, 29, 36, 37, 52, 166, 448, 2011, 3489, 4871, 6982, 10024, 16974, 33287, 47364, 58873, 126160, 234424, 382881, 524706
OFFSET
1,2
COMMENTS
Numbers k such that 10^(k+1) + (10^k-1) is a prime.
MATHEMATICA
Do[ If[ PrimeQ[10^(n + 1) + (10^n - 1)], Print[n]], {n, 9500}]
PROG
(PARI) is(n)=ispseudoprime(11*10^n-1) \\ Charles R Greathouse IV, Jun 12 2017
CROSSREFS
Cf. A096209.
Sequence in context: A075824 A228951 A108113 * A077788 A339048 A137018
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Nov 15 2005
EXTENSIONS
a(16)-a(19) from Ray Chandler, Sep 16 2013
a(20)-a(21) from P. Kurtovic submitted by Ray Chandler, Sep 17 2013
a(22)-a(24) from Kamada data by Tyler Busby, Apr 14 2024
STATUS
approved