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A102983 Numbers n such that 4*10^n + R_n + 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
2, 5, 77, 206, 1871, 3887, 11582, 20234, 60290 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also numbers n such that (37*10^n+71)/9 is prime.

a(10) > 10^5. - Robert Price, Apr 14 2015

LINKS

Table of n, a(n) for n=1..9.

Makoto Kamada, Prime numbers of the form 411...119.

Index entries for primes involving repunits.

FORMULA

a(n) =  A101718(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(37*10^n + 71)/9], Print[n]], {n, 0, 10000}]

PROG

(MAGMA) [n: n in [0..300] | IsPrime((37*10^n+71) div 9)]; // Vincenzo Librandi, Apr 15 2015

CROSSREFS

Cf. A002275, A101718.

Sequence in context: A183291 A254405 A216847 * A038583 A082080 A127997

Adjacent sequences:  A102980 A102981 A102982 * A102984 A102985 A102986

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 21 2004

EXTENSIONS

Addition of a(7)-a(8) from Kamada data by Robert Price, Dec 13 2010

a(9) from Robert Price, Apr 14 2015

STATUS

approved

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Last modified May 26 23:22 EDT 2015. Contains 257849 sequences.