OFFSET
1,1
COMMENTS
Bell(2841) has been certified to be a prime using Primo. This took 17 months on a P3-800, a P4-2400 and finally a P4-2800. There are no other terms below 6000. - Ignacio Larrosa Cañestro, Feb 13 2004
The next term, if it exists, is > 50000. - Vaclav Kotesovec, May 18 2021
No other terms < 100000. - Mathieu Gouttenoire, Oct 31 2021
LINKS
E. T. Bell, Exponential numbers, Amer. Math. Monthly, 41 (1934), 411-419.
The Prime Database, 93074010508593618333...(6499 other digits)...83885253703080601131
Eric Weisstein's World of Mathematics, Bell Number
Eric Weisstein's World of Mathematics, Integer Sequence Primes
EXAMPLE
The Bell numbers Bell(2)=2, Bell(3)=5, Bell(7)=877 etc. are primes.
MATHEMATICA
Reap[For[n = 1, n <= 3000, n++, If[PrimeQ[BellB[n]], Print[n]; Sow[n]]]][[2, 1]] (* Jean-François Alcover, Jun 05 2012 *)
Select[Range[2900], PrimeQ[BellB[#]]&] (* Harvey P. Dale, Nov 08 2012 *)
PROG
(Magma) [n: n in [0..1000]|IsPrime(Bell(n))]; // Vincenzo Librandi, Jan 30 2016
CROSSREFS
KEYWORD
hard,nonn,nice
AUTHOR
STATUS
approved