A108966 Numbers n such that repunit(n) concatenated with its 10's complement is prime; or numbers n such that (1+7*10^n+100^n)/9 is prime.

1, 5, 16, 36, 61, 149, 725, 1104, 1276, 1289, 8575

Offset

1,2

Comments

Larger values are only Fermat and Lucas PRPs.

Links

Table of n, a(n) for n=1..11.

Example

a(2)=5 because 10^5-11111 = 88889 and 1111188889 is prime.

Crossrefs

Cf. A002275.

Sequence in context: A234362 A363613 A363605 * A321019 A184635 A328506

Adjacent sequences: A108963 A108964 A108965 * A108967 A108968 A108969

Keyword

base,hard,more,nonn

Author

Jason Earls, Jul 26 2005

Status

approved