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A183177
Numbers n such that (10^(2n+1)+15*10^n-1)/3 is prime.
2
1, 7, 85, 94, 273, 356, 1077, 1797, 6758, 30232
OFFSET
1,2
COMMENTS
a(11) > 10^5. - Robert Price, Apr 21 2016
REFERENCES
C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
FORMULA
a(n) = (A077792(n)-1)/2.
MATHEMATICA
Do[If[PrimeQ[(10^(2n + 1) + 15*10^n - 1)/3], Print[n]], {n, 3000}]
PROG
(PARI) is(n)=ispseudoprime((10^(2*n+1)+15*10^n-1)/3) \\ Charles R Greathouse IV, Jun 13 2017
KEYWORD
nonn,more,base
AUTHOR
Ray Chandler, Dec 28 2010
EXTENSIONS
a(10) from Robert Price, Apr 21 2016
STATUS
approved