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Search: id:A072181
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| A072181 |
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a(1) = 1; for n >= 2, suppose a(n-1) = Product p_i^e_i and n = Product p_i^f_i, then a(n) = Product p_i^(e_i*f_i). |
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5
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| 1, 2, 6, 12, 60, 60, 420, 6720, 20160, 20160, 221760, 14192640, 184504320, 184504320, 184504320, 12679040325931499520, 215543685540835491840, 1939893169867519426560, 36857970227482869104640
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OFFSET
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1,2
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FORMULA
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Let m = Product (p_i)^(e_{i, m}), m=1, 2, ..., where p_i is i_th prime. Then a(n) = Product_{i=1..inf} (p_i)^(Product_{m =1..n} (e_{i, m})).
Let m = Product (p_i)^(e_{i, m}), m=1, 2, ..., where p_i is i_th prime. Then a(n) = Product_{i=1..inf} (p_i)^(Product_{m =1..n}[max(1, e_{i, m})]). - David Wasserman (wasserma(AT)spawar.navy.mil), Sep 07 2004
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EXAMPLE
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n=12: a(11) = 221760 = 2^6 3^2 5 7 11, 12 = 2^2 3^1, so a(12) = 2^(2*6) 3^(1*1) 5 7 11 = 14192640.
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CROSSREFS
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Adjacent sequences: A072178 A072179 A072180 this_sequence A072182 A072183 A072184
Sequence in context: A003418 A109935 A065887 this_sequence A126915 A002201 A004490
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KEYWORD
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nonn,easy,nice
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AUTHOR
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Naohiro Nomoto (n_nomoto(AT)yabumi.com), Jun 30 2002
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