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A183185 Numbers n such that 10^(2n+1)-5*10^n-1 is prime. 1
14, 22, 36, 104, 1136, 17864, 25448 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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..7.

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

Makoto Kamada, Prime numbers of the form 99...99499...99

Index entries for primes involving repunits.

FORMULA

a(n) = (A077782(n)-1)/2.

MATHEMATICA

Do[If[PrimeQ[10^(2n + 1) - 5*10^n - 1], Print[n]], {n, 3000}]

PROG

(PARI) is(n)=ispseudoprime(10^(2*n+1)-5*10^n-1) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

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

Sequence in context: A187776 A048196 A225710 * A259750 A211416 A045282

Adjacent sequences:  A183182 A183183 A183184 * A183186 A183187 A183188

KEYWORD

nonn,base

AUTHOR

Ray Chandler, Dec 28 2010

STATUS

approved

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Last modified September 23 21:14 EDT 2017. Contains 292391 sequences.