id:A087049 - OEIS Search Results

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Characteristic sequence for numbers n>=0 which are squares or have a square>1 as factor.

+0
4

1, 1, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1 (list; graph; listen)

	OFFSET	`0,1`
	COMMENT	`a(0)=1, a(1)=1, n>=2: a(n)=1 if isquarefree(n)=false else 0.` `Except for a(0)=1 and a(1)=1 this is the bit-flipped unsigned Moebius sequence \|A008683(n)\|, n>=2.` `For n>=2: a(n)=1 iff n is from A013929 (not square-free).`
	FORMULA	`a(n)=1 if n is a perfect square (A000290) or has some square > 1 as a factor, else 0.`
	EXAMPLE	`a(4)=1 because 4 is a square; a(8)=1 because 8=2^2*2.`
	CROSSREFS	`Cf. A080733, A000290(squares), A013929(not square-free).` `Sequence in context: A127239 A129186 A095901 this_sequence A118009 A113429 A133100` `Adjacent sequences: A087046 A087047 A087048 this_sequence A087050 A087051 A087052`
	KEYWORD	`nonn,easy`
	AUTHOR	`Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), Sep 08 2003`

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Last modified December 7 08:40 EST 2009. Contains 170430 sequences.

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