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Search: id:A066828
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| A066828 |
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Numbers n such that n divides the average of Prime(n-1) and Prime(n+1). |
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| 4, 5, 11, 12, 70, 72, 1053, 6459, 6460, 40083, 251742, 637320, 637322, 637330, 10553828, 69709721, 179992913, 179992922, 465769813, 1208198617, 1208198629, 3140421742, 3140421769, 3140421866, 8179002192, 8179002205, 8179002209
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OFFSET
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1,1
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COMMENT
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Each cluster of candidates is about e (2.71828...) times as large as the previous one.
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EXAMPLE
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The average of p(4) = 7 and p(6) = 13 is 10, which is divisible by 5; so 5 is a term of the sequence.
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MATHEMATICA
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a = 0; b = 1; c = 2; Do[ c = Prime[ n + 1 ]; If[ IntegerQ[ (a + c)/(2n) ], Print[ n ] ]; a = b; b = c, {n, 1, 2 10^9} ]
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CROSSREFS
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Cf. A066706.
Sequence in context: A027708 A047374 A100107 this_sequence A039006 A118423 A084812
Adjacent sequences: A066825 A066826 A066827 this_sequence A066829 A066830 A066831
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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), Jan 20 2002
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