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A183186
Numbers k such that 10^(2k+1) - 4*10^k - 1 is prime.
2
88, 112, 198, 622, 4228, 10052, 55862
OFFSET
1,1
REFERENCES
C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
FORMULA
a(n) = (A077786(n) - 1)/2.
MATHEMATICA
Do[If[PrimeQ[10^(2n + 1) - 4*10^n - 1], Print[n]], {n, 3000}]
PROG
(PARI) is(n)=ispseudoprime(10^(2*n+1)-4*10^n-1) \\ Charles R Greathouse IV, Jun 13 2017
KEYWORD
nonn,base
AUTHOR
Ray Chandler, Dec 28 2010
STATUS
approved