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Search: id:A080864
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| A080864 |
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Numbers n such that spf(n)+2 = spf(n-2), where spf=A020639 (smallest prime factor). |
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2
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| 27, 57, 87, 117, 147, 177, 205, 207, 237, 267, 297, 327, 357, 387, 415, 417, 447, 477, 507, 537, 567, 597, 625, 627, 657, 687, 717, 747, 777, 807, 835, 837, 867, 897, 927, 957, 987, 1017, 1045, 1047, 1077, 1107, 1137, 1167, 1197, 1227, 1255, 1257, 1287
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OFFSET
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1,1
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COMMENT
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(spf(n),spf(n-2)) are twin prime pairs.
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EXAMPLE
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1921=17*113, 1921-2=1919=19*101, and (17,19)=(A001359(4), A006512(4)), therefore 1921 is a term: a(74)=1921, A080863(74)=1919.
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CROSSREFS
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Cf. A080863(n)=a(n)-2, A001359, A006512.
Sequence in context: A042456 A132768 A053180 this_sequence A039459 A107580 A138610
Adjacent sequences: A080861 A080862 A080863 this_sequence A080865 A080866 A080867
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 21 2003
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