A143731 - OEIS

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A143731

Characteristic function of numbers n with at least two distinct prime factors.

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	OFFSET	`1,1`
	COMMENTS	`a(n) = 1 iff n is divisible by at least two distinct primes; otherwise 0.`
	LINKS	`Reikku Kulon, Table of n, a(n) for n = 1..10000` `Index entries for characteristic functions`
	FORMULA	`a(n) = abs(A079872(n)) = A057427(A079275(n))`
	CROSSREFS	`Cf. A079275, A079872, A000961, A001222, A091304, A073093, A001221` `Sequence in context: A011673 A104853 A079872 * A169672 A011672 A202238` `Adjacent sequences: A143728 A143729 A143730 * A143732 A143733 A143734`
	KEYWORD	`easy,nonn`
	AUTHOR	`Reikku Kulon (reikku(AT)gmail.com), Aug 30 2008`

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Last modified February 16 08:07 EST 2012. Contains 205887 sequences.