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A103078 Numbers n such that 8*10^n + 3*R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 2, 4, 9, 10, 15, 44, 55, 56, 124, 140, 279, 674, 848, 1420, 1462, 3314, 3442, 4141, 35625 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (25*10^n+17)/3 is prime.

a(21) > 10^5. - Robert Price, Oct 20 2015

LINKS

Table of n, a(n) for n=1..20.

Makoto Kamada, Prime numbers of the form 833...339.

Index entries for primes involving repunits.

FORMULA

a(n) = A101065(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(25*10^n + 17)/3], Print[n]], {n, 0, 10000}]

PROG

(PARI) for(n=1, 1e3, if(isprime((25*10^n+17)/3), print1(n", "))) \\ Altug Alkan, Oct 20 2015

CROSSREFS

Cf. A002275, A101065.

Sequence in context: A287413 A026602 A287436 * A060756 A075347 A005733

Adjacent sequences:  A103075 A103076 A103077 * A103079 A103080 A103081

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 19 2005

EXTENSIONS

a(20) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

STATUS

approved

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Last modified May 27 12:27 EDT 2020. Contains 334657 sequences. (Running on oeis4.)