A183177 - OEIS

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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

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

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.

LINKS

Table of n, a(n) for n=1..10.

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

Makoto Kamada, Prime numbers of the form 33...33833...33

Index entries for primes involving repunits.

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

CROSSREFS

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

Sequence in context: A258174 A370934 A254569 * A367351 A058795 A027459

Adjacent sequences: A183174 A183175 A183176 * A183178 A183179 A183180

KEYWORD

nonn,more,base

AUTHOR

Ray Chandler, Dec 28 2010

EXTENSIONS

a(10) from Robert Price, Apr 21 2016

STATUS

approved