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A101393 Numbers n such that 3*10^n + R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 2, 218, 692, 1805, 2207, 2873, 59135 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers such that (28*10^n+53)/9 is prime.

All except 1, 2 and 218 only probably prime. No others less than 10000.

LINKS

Table of n, a(n) for n=1..8.

Makoto Kamada, Prime numbers of the form 311...117.

Index entries for primes involving repunits.

FORMULA

a(n) = A101826(n) + 1.

EXAMPLE

n = 1, 2 are members since 37 and 317 are primes.

MATHEMATICA

Do[ If[ PrimeQ[(28*10^n+53)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A100501, A100473, A101826.

Sequence in context: A125058 A202741 A239529 * A124188 A261936 A274466

Adjacent sequences:  A101390 A101391 A101392 * A101394 A101395 A101396

KEYWORD

nonn

AUTHOR

Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005

EXTENSIONS

a(8) from Kamada data by Robert Price, Dec 13 2010

STATUS

approved

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Last modified September 19 12:57 EDT 2019. Contains 327198 sequences. (Running on oeis4.)