A102949 Numbers k such that 2*10^k + R_k + 6 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

36, 183, 330, 393, 17520, 27222

Offset

1,1

Comments

Also numbers k such that (19*10^k + 53)/9 is prime.

a(7) > 10^5. - Robert Price, Feb 07 2015

Links

Table of n, a(n) for n=1..6.

Makoto Kamada, Prime numbers of the form 211...117.

Index entries for primes involving repunits.

Formula

a(n) = A101954(n) + 1.

Mathematica

Do[ If[ PrimeQ[(19*10^n + 53)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101954.

Sequence in context: A321145 A054979 A335219 * A211733 A211744 A211753

Adjacent sequences: A102946 A102947 A102948 * A102950 A102951 A102952

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 17 2004

Extensions

Addition of a(5)-a(6) from Kamada data by Robert Price, Dec 13 2010

Status

approved