A102996 Numbers n such that 4*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 4, 26, 1271, 1412, 3328, 4676, 47051, 67664

Offset

1,1

Comments

Also numbers n such that (43*10^n+11)/9 is prime.

a(10) > 10^5. - Robert Price, Jun 01 2015

Links

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

Makoto Kamada, Prime numbers of the form 477...779.

Index entries for primes involving repunits.

Formula

a(n) = A101733(n) + 1.

Mathematica

Do[ If[ PrimeQ[(43*10^n + 11)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101733.

Sequence in context: A218077 A240040 A088888 * A358563 A189896 A095182

Adjacent sequences: A102993 A102994 A102995 * A102997 A102998 A102999

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 17 2005

Extensions

a(8) from Erik Branger, May 01 2013, submitted by Ray Chandler, Aug 16 2013

a(9) from Robert Price, Jun 01 2015

Status

approved