A102935 Numbers k such that 10^k + 4*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

1, 2, 4, 11, 13, 26, 154, 196, 436, 529, 1111, 2563, 2641, 3233, 3883, 4256, 9298, 17293, 23270, 27197, 129826

Offset

1,2

Comments

Also numbers k such that (13*10^k + 41)/9 is prime.

a(21) > 10^5. - Robert Price, Apr 19 2015

Links

Table of n, a(n) for n=1..21.

Makoto Kamada, Prime numbers of the form 144...449.

Index entries for primes involving repunits.

Formula

a(n) = A102017(n) + 1.

Mathematica

Do[ If[ PrimeQ[(13*10^n + 41)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A102017.

Sequence in context: A071069 A116439 A018525 * A287210 A236524 A295968

Adjacent sequences: A102932 A102933 A102934 * A102936 A102937 A102938

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 16 2004

Extensions

a(18)-a(20) from Kamada data by Robert Price, Dec 09 2010

a(21) from Kamada data by Tyler Busby, Apr 14 2024

Status

approved