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A051130 Indices of prime Bell numbers A000110. 3
2, 3, 7, 13, 42, 55, 2841 (list; graph; refs; listen; history; text; internal format)
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

REFERENCES

E. T. Bell, Exponential numbers, Amer. Math. Monthly, 41 (1934), 411-419.

LINKS

Table of n, a(n) for n=1..7.

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 *)

CROSSREFS

Cf. A000110, A051131.

Sequence in context: A196419 A056893 * A078749 A046062 A096263 A007996

Adjacent sequences:  A051127 A051128 A051129 * A051131 A051132 A051133

KEYWORD

hard,nonn,nice

AUTHOR

Ignacio Larrosa Cañestro

STATUS

approved

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Last modified November 21 19:01 EST 2014. Contains 249784 sequences.