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Search: id:A063884
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| A063884 |
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a(1) = 2, a(2) = 3, and a(k+1) is the least prime not already chosen that divides some a(i)*a(j)+1, where 1<=i<=j<=k. |
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1
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| 2, 3, 5, 7, 11, 13, 17, 23, 29, 19, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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"Does the sequence [above] contain every prime? Is the sequence infinite?" ... "The sequence of problem [above] is not even known to be infinite, though it almost surely contains every prime. We do not know whether anyone has attacked the problem computationally; perhaps you, the reader, would like to give it a try. The problem is due to M. Newman at the Australian Nation University." - Crandall and Pomerance
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REFERENCES
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R. Crandall and C. Pomerance, Prime Numbers: A Computational Perspective, Springer, NY, 2001; see p. 6.
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EXAMPLE
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a(3) is equal to 5 because a(1)*a(1)+1 = 2*2+1 = 5.
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MATHEMATICA
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a = {2, 3}; Do[l = Length[a]; a = Append[ a, Complement[ Union[Flatten[ Table[ Transpose[ FactorInteger[ a[[i]]*a[[j]] + 1]] [[1]], {i, 1, l}, {j, 1, i} ]]], a] [[1]]], {n, 3, 100} ]; a
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CROSSREFS
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Cf. A000040.
Sequence in context: A088415 A139054 A003309 this_sequence A040067 A040087 A040065
Adjacent sequences: A063881 A063882 A063883 this_sequence A063885 A063886 A063887
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 04 2001
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