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Search: id:A103845
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| A103845 |
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Product of first n Lucas numbers, plus one. |
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+0
1
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| 1, 2, 4, 13, 85, 925, 16633, 482329, 22669417, 1722875617, 211913700769, 42170826452833, 13579006117811905, 7074662187380001985, 5963940223961341672513, 8134814465483270041306369
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OFFSET
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0,2
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COMMENT
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Prime for n = 1, 3, 6; semiprime for n = 2, 4, 7, 8, 9, 10, 13, 14, 15, 23, 26. a(n) asymptotic to Phi^A000217(n).
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FORMULA
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a(n) = Product[Lucasi[k], {k, 1, n}]+1. a(n) = Product[A000217(k), {k, 1, n}]+1.
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EXAMPLE
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a(10) = 1 * 3 * 4 * 7 * 11 * 18 * 29 * 47 * 76 * 123 + 1 = 211913700769 = 349 * 607202581 which is semiprime.
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CROSSREFS
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Cf. A000045, A000204, A000217, A052449, A103815.
Sequence in context: A020097 A139149 A132786 this_sequence A055463 A091957 A056678
Adjacent sequences: A103842 A103843 A103844 this_sequence A103846 A103847 A103848
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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), Mar 30 2005
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