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Search: id:A103746
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| A103746 |
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Numbers n such that prime(n)*prime(n+1) - 1 is semiprime. |
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+0
5
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| 2, 3, 5, 10, 13, 20, 33, 60, 89, 109, 116, 138, 144, 152, 182, 189, 212, 223, 253, 258, 297, 320, 336, 350, 353, 375, 390, 418, 422, 487, 492, 498, 501, 549, 567, 579, 592, 616, 654, 671, 704, 755, 799, 800, 812, 826, 874, 893, 917, 921, 948, 951, 957, 967
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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prime(10)*prime(11) - 1 = 29*31 - 1 = 898 = 2*449, hence 10 is a term.
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PROGRAM
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(PARI) for(n=1, 1000, if(bigomega(prime(n)*prime(n+1)-1)==2, print1(n, ", ")))
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CROSSREFS
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Cf. A001358, A006881, A103533.
Sequence in context: A005677 A162404 A084760 this_sequence A071848 A120938 A120610
Adjacent sequences: A103743 A103744 A103745 this_sequence A103747 A103748 A103749
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KEYWORD
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nonn,easy
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AUTHOR
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Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Mar 29 2005
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