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Search: id:A118476
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| A118476 |
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a(0) = 1; a(n) is least k with n prime factors and k > n*a(n-1). |
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+0
1
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OFFSET
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0,2
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COMMENT
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This is a super-polynomial function, as for positive n, a(n) > n!.
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LINKS
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Eric Weisstein's World of Mathematics, Almost Prime.
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FORMULA
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a(0) = 1; a(n) least n-almost prime > n*a(n-1).
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EXAMPLE
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a(1) = 2 because 2 is the smallest prime (integer with 1 prime factor) greater than 1 * 1 = 1.
a(2) = 6 because 6 = 2 * 3 is the smallest semiprime (integer with 2 prime factors) greater than 2 * 2 = 4.
a(3) = 18 because 18 = 2 * 3^2 is the smallest 3-almost prime (integer with 3 prime factors) greater than 3 * 4 = 12.
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CROSSREFS
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Cf. A000040, A001358, A055496, A076656.
Sequence in context: A113844 A141580 A007869 this_sequence A118455 A053505 A000138
Adjacent sequences: A118473 A118474 A118475 this_sequence A118477 A118478 A118479
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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 04 2006
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