A299382 Numbers k such that k * 19^k - 1 is prime.

12, 410, 33890, 91850, 146478, 189620, 280524

Offset: 1

Author

Tim Johannes Ohrtmann, Feb 08 2018

Keywords

• nonn
• more
• hard

Comments

a(8) > 400000.

Links

• Steven Harvey, Generalized Woodall Search.
• Wikipedia, Woodall number.

Crossrefs

Numbers n such that n * b^n - 1 is prime: A008864 (b=1), A002234 (b=2), A006553 (b=3), A086661 (b=4), A059676 (b=5), A059675 (b=6), A242200 (b=7), A242201 (b=8), A242202 (b=9), A059671 (b=10), A299374 (b=11), A299375 (b=12), A299376 (b=13), A299377 (b=14), A299378 (b=15), A299379 (b=16), A299380 (b=17), A299381 (b=18), this sequence (b=19), A299383 (b=20).

Programs

Magma

[n: n in [1..10000] |IsPrime(n*19^n-1)];

Mathematica

Select[Range[1, 10000], PrimeQ[n*19^n-1] &]

PARI

for(n=1, 10000, if(isprime(n*19^n-1), print1(n", ")))