id:A070238 - OEIS Search Results

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Sign of core(n)-phi(n) where core(n) is the square-free part of n and phi the Euler totient function.

+0
1

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; listen)

	OFFSET	`1,1`
	COMMENT	`sum(k=1,a(k))>0 for n>1.`
	FORMULA	`For almost n, a(n)=2mu(n)^2-1=2A008683(n)-1. Below 1000, there are only 4 exceptions : n=420, 660, 780, 840.`
	PROGRAM	`(PARI) for(n=1, 100, print1(sign(core(n)-eulerphi(n)), ", "))`
	CROSSREFS	`Sequence in context: A165586 A165476 A165596 this_sequence A103131 A057427 A057428` `Adjacent sequences: A070235 A070236 A070237 this_sequence A070239 A070240 A070241`
	KEYWORD	`easy,sign`
	AUTHOR	`Benoit Cloitre (benoit7848c(AT)orange.fr), May 08 2002`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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