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A102956 Numbers n such that 2*10^n + 5*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 82, 322, 733, 2431, 8386, 15886, 19912 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (23*10^n+31)/9 is prime.

a(9) > 10^5. - Robert Price, Feb 06 2015

LINKS

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

Makoto Kamada, Prime numbers of the form 255...559.

Index entries for primes involving repunits.

FORMULA

a(n) = A101963(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(23*10^n + 31)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101963.

Sequence in context: A227704 A248405 A116341 * A031696 A005972 A082972

Adjacent sequences:  A102953 A102954 A102955 * A102957 A102958 A102959

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 17 2004

EXTENSIONS

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

STATUS

approved

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Last modified March 22 10:07 EDT 2019. Contains 321421 sequences. (Running on oeis4.)