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Search: id:A106627
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| A106627 |
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Product L(n)*L_4(n), where L(n) are Lucas numbers and L_4(n) are Lucas 4-step numbers. |
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| 8, 1, 9, 28, 105, 286, 918, 2871, 8977, 27892, 87084, 271635, 847182, 2641991, 8240325, 25700488, 80156033, 249994997, 779700654, 2431777739, 7584375260
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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a(n) is semiprime iff n is an element of A001606 (an index of a prime Lucas number) and an element of A104577 (an index of a prime Lucas 4-step number). The only known such are n = 2, 8, 16, 19, 71, (through 145858).
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FORMULA
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a(n) = A000032(n) * A073817(n).
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EXAMPLE
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a(0) = 8 because L(0) * L_4(0) = 2 * 4.
a(1) = 1 because L(1) * L_4(1) = 1 * 1.
a(2) = 9 because L(2) * L_4(2) = 3 * 3.
a(3) = 28 because L(3) * L_4(3) = 4 * 7.
a(4) = 105 because L(4) * L_4(4) = 7 * 15.
a(5) = 286 because L(5) * L_4(5) = 11 * 26.
a(6) = 918 because L(6) * L_4(6) = 18 * 51.
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CROSSREFS
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Cf. A000032, A000040, A001358, A001606, A073446, A073817, A104576.
Sequence in context: A019864 A021126 A091557 this_sequence A160925 A099614 A032012
Adjacent sequences: A106624 A106625 A106626 this_sequence A106628 A106629 A106630
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), May 11 2005
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