A102970 Numbers n such that 3*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 3, 6, 12, 36, 39, 44, 90, 258, 512, 1482, 2378, 2406, 3224, 3378, 3876, 4161, 5510, 7425, 97242

Offset

1,1

Comments

Also numbers n such that (31*10^n+41)/9 is prime.

a(21) > 10^5. - Robert Price, Apr 04 2015

Links

Table of n, a(n) for n=1..20.

Makoto Kamada, Prime numbers of the form 344...449.

Index entries for primes involving repunits.

Formula

a(n) = A101834(n) + 1.

Mathematica

Do[ If[ PrimeQ[(31*10^n+41)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101834.

Sequence in context: A213242 A243299 A096746 * A144771 A187013 A295324

Adjacent sequences: A102967 A102968 A102969 * A102971 A102972 A102973

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 17 2004

Extensions

a(20) from Robert Price, Apr 04 2015

Status

approved