A183174 Numbers n such that (10^(2n+1)-6*10^n-1)/3 is prime.

1, 3, 7, 61, 90, 92, 269, 298, 321, 371, 776, 1567, 2384, 2566, 3088, 5866, 8051, 9498, 12635, 24512, 32521, 43982

Offset

1,2

Comments

a(23) > 10^5. - Robert Price, Jan 29 2016

References

C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.

Links

Table of n, a(n) for n=1..22.

Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's)

Makoto Kamada, Prime numbers of the form 33...33133...33

Index entries for primes involving repunits.

Formula

a(n) = (A077775(n)-1)/2.

Mathematica

Do[If[PrimeQ[(10^(2n + 1) - 6*10^n - 1)/3], Print[n]], {n, 3000}]

Prog

(PARI) for(n=1, 1e3, if(ispseudoprime((10^(2*n+1)-6*10^n-1)/3), print1(n", "))) \\ Charles R Greathouse IV, Jul 15 2011

Crossrefs

Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.

Sequence in context: A242380 A225195 A084289 * A329966 A255669 A258184

Adjacent sequences: A183171 A183172 A183173 * A183175 A183176 A183177

Keyword

nonn,base

Author

Ray Chandler, Dec 28 2010

Extensions

a(21)-a(22) from Robert Price, Jan 29 2016

Status

approved