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A102973 Numbers n such that 3*10^n + 5*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 2, 3, 5, 8, 14, 77, 195, 218, 957, 1052, 1163, 1485, 1731, 1970, 3237, 17354, 85964 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (32*10^n+31)/9 is prime.

a(19) > 10^5. - Robert Price, May 31 2015

LINKS

Table of n, a(n) for n=1..18.

Makoto Kamada, Prime numbers of the form 355...559.

Index entries for primes involving repunits.

FORMULA

a(n) = A101838(n-1) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(32*10^n+31)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101838.

Sequence in context: A196118 A104880 A152478 * A066372 A058519 A181065

Adjacent sequences:  A102970 A102971 A102972 * A102974 A102975 A102976

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 17 2004

EXTENSIONS

Addition of a(17) from Kamada data by Robert Price, Dec 12 2010

a(18) from Robert Price, May 31 2015

STATUS

approved

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Last modified July 28 20:29 EDT 2015. Contains 260095 sequences.