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A102980 Numbers n such that 3*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
2, 3, 6, 17, 20, 45, 57, 78, 119, 137, 509, 710, 1127, 1518, 1761, 3086, 3147, 9926, 19854, 27842, 46799, 49682, 68718, 100542, 106649, 191073 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also numbers n such that (35*10^n+1)/9 is prime.

LINKS

Table of n, a(n) for n=1..26.

Makoto Kamada, Prime numbers of the form 388...889.

Index entries for primes involving repunits.

FORMULA

a(n) = A101847(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(35*10^n + 1)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101847.

Sequence in context: A174118 A006449 A230146 * A181185 A241945 A018284

Adjacent sequences:  A102977 A102978 A102979 * A102981 A102982 A102983

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 21 2004

EXTENSIONS

Addition of a(19)-a(26) from Kamada data by Robert Price, Dec 08 2010

STATUS

approved

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Last modified November 29 02:34 EST 2020. Contains 338756 sequences. (Running on oeis4.)