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A070238
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Sign of core(n)-phi(n) where core(n) is the squarefree part of n and phi the Euler totient function.
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0
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0, 1, 1, -1, 1, 1, 1, -1, -1, 1, 1, -1, 1, 1, 1, -1, 1, -1, 1, -1, 1, 1, 1, -1, -1, 1, -1, -1, 1, 1, 1, -1, 1, 1, 1, -1, 1, 1, 1, -1, 1, 1, 1, -1, -1, 1, 1, -1, -1, -1, 1, -1, 1, -1, 1, -1, 1, 1, 1, -1, 1, 1, -1, -1, 1, 1, 1, -1, 1, 1, 1, -1, 1, 1, -1, -1, 1, 1, 1, -1, -1, 1, 1, -1, 1, 1, 1, -1, 1, -1, 1, -1, 1, 1, 1, -1, 1, -1, -1, -1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| sum(k=1,a(k))>0 for n>1.
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FORMULA
| For almost n, a(n)=2*mu(n)^2-1=2*A008683(n)-1. Below 1000, there are only 4 exceptions : n=420, 660, 780, 840.
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PROG
| (PARI) for(n=1, 100, print1(sign(core(n)-eulerphi(n)), ", "))
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CROSSREFS
| Sequence in context: A134824 A165476 A165596 * A062157 A103131 A112347
Adjacent sequences: A070235 A070236 A070237 * A070239 A070240 A070241
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KEYWORD
| easy,sign
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), May 08 2002
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