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A051130
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Indices of prime Bell numbers A000110.
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3
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OFFSET
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1,1
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COMMENTS
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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
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REFERENCES
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E. T. Bell, Exponential numbers, Amer. Math. Monthly, 41 (1934), 411-419.
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LINKS
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Table of n, a(n) for n=1..7.
Eric Weisstein's World of Mathematics, Bell Numbers
Eric Weisstein's World of Mathematics, Bell Number
Eric Weisstein's World of Mathematics, Integer Sequence Primes
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EXAMPLE
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The Bell numbers Bell(2)=2, Bell(3)=5, Bell(7)=877 etc. are primes.
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MATHEMATICA
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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 *)
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CROSSREFS
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Cf. A000110, A051131.
Sequence in context: A196419 A056893 * A078749 A046062 A096263 A007996
Adjacent sequences: A051127 A051128 A051129 * A051131 A051132 A051133
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KEYWORD
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hard,nonn,nice
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AUTHOR
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Ignacio Larrosa Canestro (ignacio.larrosa(AT)eresmas.net)
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STATUS
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approved
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