A102989 - OEIS

A102989

Numbers n such that 4*10^n + 3*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 3, 5, 6, 8, 15, 26, 53, 60, 97, 183, 205, 302, 396, 456, 467, 607, 828, 1860, 2743, 4273, 4781, 5712, 6038, 6637, 9222, 10832, 18865, 25848, 42247, 48547, 87565, 95588

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OFFSET

1,2

COMMENTS

Also numbers n such that (13*10^n+11)/3 is prime.

a(34) > 10^5. - Robert Price, May 11 2015

LINKS

Table of n, a(n) for n=1..33.

Makoto Kamada, Prime numbers of the form 433...337.

Index entries for primes involving repunits.

FORMULA

a(n) = A101724(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(13*10^n + 11)/3], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101724.

Sequence in context: A039869 A076210 A039014 * A005623 A335110 A152989

Adjacent sequences: A102986 A102987 A102988 * A102990 A102991 A102992

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 17 2005

EXTENSIONS

Addition of a(27)-a(29) from Kamada data by Robert Price, Dec 08 2010

a(30)-a(31) from Erik Branger, May 01 2013, submitted by Ray Chandler, Aug 16 2013

a(32)-a(33) from Robert Price, May 11 2015

STATUS

approved