A059671 Numbers n such that n*10^n - 1 is prime.

2, 3, 8, 11, 15, 39, 60, 72, 77, 117, 183, 252, 396, 1745, 2843, 4665, 5364, 524427

Offset: 1

Author

Robert G. Wilson v, Feb 05 2001

Keywords

• nonn

Comments

No further terms up to 500000 (see Harvey link). - Ray Chandler, Apr 10 2016

References

• J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 117, p. 41, Ellipses, Paris 2008.

Links

• Steven Harvey, Generalized Woodall Search
• Prime Pages, Top 20, Generalized Woodall
• Prime-Wiki, Generalized Woodall primes of the form n*10^n-1

Programs

Mathematica

Do[ If[ PrimeQ[ n*10^n - 1 ], Print[ n ] ], {n, 1, 2500} ]

PARI

is(n)=ispseudoprime(n*10^n-1) \\ Charles R Greathouse IV, Mar 01 2017

Extensions

a(15) - a(17) from Farideh Firoozbakht, Apr 01 2009

a(18) communicated by Jeppe Stig Nielsen, Apr 03 2023