A102976 Numbers k such that 3*10^k + 7*R_k - 6 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

1, 5, 71, 112, 115, 173, 263, 310, 358, 10499, 22925, 37957, 254195, 463649

Offset

1,2

Comments

Also numbers k such that (34*10^k-61)/9 is prime.

a(15) > 8*10^5. - Jason H Parker, Sep 30 2021

Links

Table of n, a(n) for n=1..14.

Makoto Kamada, Prime numbers of the form 377...771.

Index entries for primes involving repunits.

Formula

a(n) = A101841(n) + 1.

Mathematica

Do[ If[ PrimeQ[(34*10^k-61)/9], Print[k]], {k, 1, 10000}]

Crossrefs

Cf. A002275, A101841.

Sequence in context: A248367 A157860 A125242 * A141852 A142052 A139930

Adjacent sequences: A102973 A102974 A102975 * A102977 A102978 A102979

Keyword

nonn,more

Author

Robert G. Wilson v, Dec 17 2004

Extensions

Addition of a(10)-a(11) from Kamada data by Robert Price, Dec 13 2010

a(12) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

a(13) from Jason H Parker, Jun 14 2019

0 removed by Georg Fischer, Jan 03 2021

a(14) from Jason H Parker, Sep 30 2021

Status

approved