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A103082 Numbers n such that 8*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 1, 4, 13, 37, 46, 106, 139, 469, 5695, 56281, 58669 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Also numbers n such that (76*10^n+41)/9 is prime.

a(13) > 10^5. - Robert Price, Oct 18 2015

LINKS

Table of n, a(n) for n=1..12.

Makoto Kamada, Prime numbers of the form 844...449.

Index entries for primes involving repunits.

FORMULA

a(n) = A101069(n-1) + 1 for n>1.

MATHEMATICA

Do[ If[ PrimeQ[(76*10^n + 41)/9], Print[n]], {n, 0, 10000}]

PROG

(PARI) for(n=0, 1e5, if(isprime(k=(76*10^n+41)/9), print1(n", "))) \\ Altug Alkan, Oct 19 2015

CROSSREFS

Cf. A002275, A101069.

Sequence in context: A222425 A222189 A003727 * A279111 A299111 A324250

Adjacent sequences:  A103079 A103080 A103081 * A103083 A103084 A103085

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 19 2005

EXTENSIONS

Inserted a(1)=0 and added a(11)-a(12) by Robert Price, Oct 18 2015

STATUS

approved

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Last modified April 23 07:51 EDT 2019. Contains 322381 sequences. (Running on oeis4.)