A103050 - OEIS

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A103050

Numbers n such that 7*10^n + R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1

1, 7, 133, 938, 17666, 20864, 56756

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OFFSET

1,2

COMMENTS

Also numbers n such that (64*10^n+17)/9 is prime.

a(8) > 10^5. - Robert Price, Sep 18 2015

LINKS

Table of n, a(n) for n=1..7.

Makoto Kamada, Prime numbers of the form 711...113.

Index entries for primes involving repunits.

FORMULA

a(n) = A101131(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(64*10^n + 17)/9], Print[n]], {n, 0, 10000}]

PROG

(PARI) is(n)=isprime((64*10^n + 17)/9) \\ Anders Hellström, Sep 18 2015

CROSSREFS

Cf. A002275, A101131.

Sequence in context: A305955 A377006 A051832 * A110111 A245318 A370782

Adjacent sequences: A103047 A103048 A103049 * A103051 A103052 A103053

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 19 2005

EXTENSIONS

a(5)-a(6) from Kamada data by Robert Price, Dec 14 2010

a(7) from Robert Price, Sep 18 2015

STATUS

approved