A059671 - OEIS

%I #16 Apr 03 2023 12:00:12

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

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

%C No further terms up to 500000 (see Harvey link). - _Ray Chandler_, Apr 10 2016

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

%H Steven Harvey, <a href="http://harvey563.tripod.com/GeneralizedWoodallPrimes.txt">Generalized Woodall Search</a>

%H Prime Pages, <a href="https://t5k.org/top20/page.php?id=45">Top 20, Generalized Woodall</a>

%H Prime-Wiki, <a href="https://www.rieselprime.de/ziki/Woodall_prime_10">Generalized Woodall primes of the form n*10^n-1</a>

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

%o (PARI) is(n)=ispseudoprime(n*10^n-1) \\ _Charles R Greathouse IV_, Mar 01 2017

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Feb 05 2001

%E a(15) - a(17) from _Farideh Firoozbakht_, Apr 01 2009

%E a(18) communicated by _Jeppe Stig Nielsen_, Apr 03 2023