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Search: id:A128538
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| A128538 |
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Number of prime factors (with multiplicity) of lucky numbers. |
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+0
1
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| 0, 1, 1, 2, 1, 2, 2, 2, 1, 2, 1, 1, 2, 2, 3, 1, 2, 1, 3, 1, 2, 2, 3, 3, 2
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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a(n) = 0 iff n = 1. a(n) = 1 iff n-th lucky number is prime iff A000959(n) is in A031157 Numbers that are both lucky and prime. a(n) > 1 iff n-th lucky number is composite iff A000959(n) is in A031879 Composite lucky numbers [technically, A031879 should not begin with 1]. a(n) = 2 iff n-th lucky number is semiprime iff A000959(n) is in A001358. a(n) = 3 iff n-th lucky number has 3 prime factors (with multiplicity) iff A000959(n) is in A014612.
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FORMULA
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a(n) = A001222(A000959(n)).
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CROSSREFS
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Cf. A000040, A000959, A001222, A001358, A014612, A031157, A031879.
Adjacent sequences: A128535 A128536 A128537 this_sequence A128539 A128540 A128541
Sequence in context: A110244 A055188 A084989 this_sequence A115588 A105220 A083654
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost2(AT)yahoo.com), May 07 2007
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