A102980 Numbers n such that 3*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 3, 6, 17, 20, 45, 57, 78, 119, 137, 509, 710, 1127, 1518, 1761, 3086, 3147, 9926, 19854, 27842, 46799, 49682, 68718, 100542, 106649, 191073

Offset

1,1

Comments

Also numbers n such that (35*10^n+1)/9 is prime.

Links

Table of n, a(n) for n=1..26.

Makoto Kamada, Prime numbers of the form 388...889.

Index entries for primes involving repunits.

Formula

a(n) = A101847(n) + 1.

Mathematica

Do[ If[ PrimeQ[(35*10^n + 1)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101847.

Sequence in context: A006449 A003323 A230146 * A181185 A241945 A018284

Adjacent sequences: A102977 A102978 A102979 * A102981 A102982 A102983

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 21 2004

Extensions

Addition of a(19)-a(26) from Kamada data by Robert Price, Dec 08 2010

Status

approved