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A128269
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a(1)=1. a(n) = LCM((number of earlier terms which are coprime to n),(sum of the earlier terms which are coprime to n)).
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2
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1, 1, 2, 2, 12, 2, 60, 2, 30, 2, 570, 2, 4116, 2, 144, 2, 39600, 2, 747694, 2, 9720308, 2, 115638138, 2, 1261104380, 2, 3814717230, 2, 137331022698, 2, 2137994925180, 2, 8901006912, 2, 274682981784, 2, 46154014360092, 2, 29022598622, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| For n > 2, a(n) is even since by induction the sum of coprimes is 1+1+some even numbers. Therefore a(n) = 2 for even n > 2 since only the 1's are coprime.
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LINKS
| H. v. Eitzen, Table of n, a(n) for n=1..10000
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EXAMPLE
| Among {a(1),a(2),...a(8)} the terms which are coprime to 9 are a(1)=a(2)=1 and a(3)=a(4)=a(6)=a(8)=2. There are 6 such terms. And the sum of these terms is 10. So a(8) = LCM(6,10) = 30.
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CROSSREFS
| Cf. A128268.
Sequence in context: A095215 A076976 A058044 * A109813 A086595 A013605
Adjacent sequences: A128266 A128267 A128268 * A128270 A128271 A128272
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KEYWORD
| nonn
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AUTHOR
| Leroy Quet Feb 22 2007
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EXTENSIONS
| More terms copied from b-file by Hagen von Eitzen (math(AT)von-eitzen.de), Jun 24 2009
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