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A183176
Numbers k such that (10^(2k+1) + 12*10^k - 1)/3 is prime.
2
1, 3, 7, 11, 13, 17, 29, 31, 33, 77, 933, 1555, 11758, 117707
OFFSET
1,2
COMMENTS
a(14) > 100000. - Robert Price, Dec 29 2016
REFERENCES
C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
FORMULA
a(n) = (A077790(n) - 1)/2.
MATHEMATICA
Do[If[PrimeQ[(10^(2n + 1) + 12*10^n - 1)/3], Print[n]], {n, 3000}]
PROG
(PARI) is(n)=ispseudoprime((10^(2*n+1)+12*10^n-1)/3) \\ Charles R Greathouse IV, Jun 13 2017
KEYWORD
nonn,more,base
AUTHOR
Ray Chandler, Dec 28 2010
EXTENSIONS
a(14) from Robert Price, Oct 30 2023
STATUS
approved