A110920 Integers n such that 2*10^n + 81 is a prime number.

0, 1, 2, 3, 6, 7, 8, 15, 36, 38, 51, 168, 1000, 2955, 8151, 16456, 17902, 18784, 24948, 28731, 87144

Offset

1,3

Comments

See Kamada link - primecount.txt for terms, primesize.txt for discovery details including probable or proved primes - search on "20081".

a(22) > 10^5. - Robert Price, Jan 19 2017

Links

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

Makoto Kamada, List of near-repdigit-related prime numbers.

Index entries for primes involving repunits.

Example

n = 3 is a term because 2*10^3 + 81 = 2*1000 + 81 = 2000 + 81 = 2081 and 2081 is prime.

Crossrefs

Cf. A049054, A088274, A088275, A095688, A107083, A108049, A108050, A108052, A108054.

Sequence in context: A030164 A066646 A215488 * A296414 A267590 A145266

Adjacent sequences: A110917 A110918 A110919 * A110921 A110922 A110923

Keyword

more,nonn

Author

Julien Peter Benney (jpbenney(AT)ftml.net), Oct 04 2005

Extensions

a(15)-a(18) from Kamada link by Ray Chandler, Dec 23 2010

a(1)-a(2) prepended by Robert Price, Jan 19 2017

a(19)-a(21) from Robert Price, Jan 19 2017

Status

approved