A183176 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

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.

LINKS

Table of n, a(n) for n=1..14.

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

Makoto Kamada, Prime numbers of the form 33...33733...33.

Index entries for primes involving repunits.

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

CROSSREFS

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

Sequence in context: A020618 A184865 A055211 * A045417 A260379 A045418

Adjacent sequences: A183173 A183174 A183175 * A183177 A183178 A183179

KEYWORD

nonn,more,base

AUTHOR

Ray Chandler, Dec 28 2010

EXTENSIONS

a(14) from Robert Price, Oct 30 2023

STATUS

approved