A183181
Numbers k such that (7*10^(2*k+1) - 9*10^k - 7)/9 is prime.
Original entry on oeis.org
4, 5, 8, 11, 1244, 1685, 2009, 14657, 15118, 20332, 50830, 75062
Offset: 1
- C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
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Do[If[PrimeQ[(7*10^(2n + 1) - 9*10^n - 7)/9], Print[n]], {n, 3000}]
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is(n)=ispseudoprime((7*10^(2*n+1)-9*10^n-7)/9) \\ Charles R Greathouse IV, Jun 13 2017
A183182
Numbers k such that (7*10^(2*k+1) + 9*10^k - 7)/9 is prime.
Original entry on oeis.org
1, 3, 39, 54, 168, 240, 5328, 6159, 24675, 52227, 113887
Offset: 1
- C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
-
Do[If[PrimeQ[(7*10^(2n + 1) + 9*10^n - 7)/9], Print[n]], {n, 3000}]
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is(n)=ispseudoprime((7*10^(2*n+1)+9*10^n-7)/9) \\ Charles R Greathouse IV, Jun 13 2017
A183183
Numbers n such that (7*10^(2n+1)+18*10^n-7)/9 is prime.
Original entry on oeis.org
1, 2, 8, 19, 20, 212, 280, 887, 1021, 5515, 8116, 11852
Offset: 1
- C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
-
Do[If[PrimeQ[(7*10^(2n + 1) + 18*10^n - 7)/9], Print[n]], {n, 3000}]
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is(n)=ispseudoprime((7*10^(2*n+1)+18*10^n-7)/9) \\ Charles R Greathouse IV, Jun 13 2017
A183185
Numbers n such that 10^(2n+1)-5*10^n-1 is prime.
Original entry on oeis.org
14, 22, 36, 104, 1136, 17864, 25448
Offset: 1
- C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
-
Do[If[PrimeQ[10^(2n + 1) - 5*10^n - 1], Print[n]], {n, 3000}]
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is(n)=ispseudoprime(10^(2*n+1)-5*10^n-1) \\ Charles R Greathouse IV, Jun 13 2017
A183186
Numbers k such that 10^(2k+1) - 4*10^k - 1 is prime.
Original entry on oeis.org
88, 112, 198, 622, 4228, 10052, 55862
Offset: 1
- C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
-
Do[If[PrimeQ[10^(2n + 1) - 4*10^n - 1], Print[n]], {n, 3000}]
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is(n)=ispseudoprime(10^(2*n+1)-4*10^n-1) \\ Charles R Greathouse IV, Jun 13 2017
A077787
Numbers k such that (10^k - 1)/9 + 5*10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime).
Original entry on oeis.org
21, 29, 81, 119, 321, 825, 1121, 2579, 3693
Offset: 1
21 is a term because (10^21 - 1)/9 + 5*10^10 = 111111111161111111111.
- C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
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Do[ If[ PrimeQ[(10^n + 45*10^Floor[n/2] - 1)/9], Print[n]], {n, 3, 4000, 2}] (* Robert G. Wilson v, Dec 16 2005 *)
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