A109800 Numbers n such that 55*10^n + 1 is prime.

2, 3, 7, 9, 33, 61, 93, 112, 284, 615, 1293, 2558, 2925, 5961, 6454, 7960, 17521, 40838

Offset: 1

Author

Jason Earls, Aug 15 2005

Keywords

• more
• nonn

Comments

All values proved prime. No more up to 25000. Primality proof for the largest: PFGW Version 20041001.Win_Stable (v1.2 RC1b) [FFT v23.8] Primality testing 55*10^17521+1 [N-1, Brillhart-Lehmer-Selfridge] Running N-1 test using base 3 Calling Brillhart-Lehmer-Selfridge with factored part 69.89% 55*10^17521+1 is prime! (48.1892s+0.1481s)

Crossrefs

Cf. A056806, A056805.

Programs

PARI

is(n)=ispseudoprime(55*10^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(18) from Kamada data by Tyler Busby, Apr 24 2024