A102994 Numbers n such that 4*10^n + 6*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 7, 9, 14, 24, 45, 49, 73, 74, 232, 338, 397, 504, 1063, 2817, 5305, 16768, 27060

Offset

1,2

Comments

Also numbers n such that (14*10^n-17)/3 is prime.

a(20) > 10^5. - Robert Price, May 27 2015

Links

Table of n, a(n) for n=1..19.

Makoto Kamada, Prime numbers of the form 466...661.

Index entries for primes involving repunits.

Formula

a(n) = A101729(n) + 1.

Mathematica

Do[ If[ PrimeQ[(14*10^n - 17)/3], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101729.

Sequence in context: A074244 A190565 A341631 * A226824 A168132 A211280

Adjacent sequences: A102991 A102992 A102993 * A102995 A102996 A102997

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 17 2005

Extensions

Addition of a(18)-a(19) from Kamada data by Robert Price, Dec 10 2010

Status

approved