A102995 Numbers n such that 4*10^n + 7*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 22, 925, 2340, 15955, 16098, 55512, 82752

Offset

1,2

Comments

Also numbers n such that (43*10^n-61)/9 is prime.

a(9) > 10^5. - Robert Price, Jun 01 2015

Links

Table of n, a(n) for n=1..8.

Makoto Kamada, Prime numbers of the form 477...771.

Index entries for primes involving repunits.

Formula

a(n) = A101732(n) + 1.

Mathematica

Do[ If[ PrimeQ[(43*10^n - 61)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101732.

Sequence in context: A345456 A322930 A200575 * A211887 A041927 A041924

Adjacent sequences: A102992 A102993 A102994 * A102996 A102997 A102998

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 17 2005

Extensions

Two more PRP terms from Serge Batalov, Feb 15 2009

a(7)-a(8) from Robert Price, Jun 01 2015

Status

approved