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A103097 Numbers n such that 9*10^n + 4*R_n - 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
2, 4, 8, 2960, 4571, 5201, 17864, 21922, 89375 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also numbers n such that (85*10^n-31)/9 is prime.

a(10) > 10^5. - Robert Price, Nov 07 2015

LINKS

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

Makoto Kamada, Prime numbers of the form 944...441.

Index entries for primes involving repunits.

FORMULA

a(n) = A101006(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(85*10^n - 31)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101006.

Sequence in context: A012456 A071686 A296742 * A062286 A071071 A195729

Adjacent sequences:  A103094 A103095 A103096 * A103098 A103099 A103100

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 19 2005

EXTENSIONS

a(7)-a(8) from Kamada data by Robert Price, Dec 14 2010

a(9) from Robert Price, Nov 07 2015

STATUS

approved

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Last modified October 18 22:57 EDT 2019. Contains 328211 sequences. (Running on oeis4.)