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Search: id:A065330
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| A065330 |
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a(n) = Max { k | gcd(n, k) = k and gcd(k, 6) = 1 }. |
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+0
9
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| 1, 1, 1, 1, 5, 1, 7, 1, 1, 5, 11, 1, 13, 7, 5, 1, 17, 1, 19, 5, 7, 11, 23, 1, 25, 13, 1, 7, 29, 5, 31, 1, 11, 17, 35, 1, 37, 19, 13, 5, 41, 7, 43, 11, 5, 23, 47, 1, 49, 25, 17, 13, 53, 1, 55, 7, 19, 29, 59, 5, 61, 31, 7, 1, 65, 11, 67, 17, 23, 35, 71, 1, 73, 37, 25, 19, 77, 13, 79, 5, 1
(list; graph; listen)
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OFFSET
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1,5
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COMMENT
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a(n) * A065331(n) = n.
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FORMULA
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Multiplicative with a(2^e)=1, a(3^e)=1, a(p^e)=p^e, p>3. - Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 02 2001
A106799(n) = A001222(a(n)). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), May 19 2005
a(1)=1; then a(2n)=a(n), a(2n+1)=a((2n+1)/3) if 2n+1 is divisible by 3, a(2n+1)=2n+1 otherwise - Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 04 2007
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EXAMPLE
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a(30) = 5.
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MATHEMATICA
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f[n_] := Times @@ (First@#^Last@# & /@ Select[FactorInteger@n, First@# != 2 && First@# != 3 &]); Array[f, 81] (* Robert G. Wilson v Aug 18 2006 *)
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PROGRAM
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(PARI) a(n)=if(n<2, 1, if(n%2, if(n%3, n, a(n/3)), a(n/2))) - Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 04 2007
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CROSSREFS
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A065331
Cf. A000265, A038502.
Sequence in context: A007397 A052345 A111008 this_sequence A140215 A068328 A109375
Adjacent sequences: A065327 A065328 A065329 this_sequence A065331 A065332 A065333
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KEYWORD
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mult,nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 29 2001
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