A099104 - OEIS

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A099104

Characteristic function of badly sieved numbers (A066680).

0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	COMMENTS	`a(A066680(n)) = 1;` `A066683(n)=Sum(a(k):1<=k<=n); A066682(n)=a(n)*A066683(n).`
	LINKS	`Index entries for characteristic functions`
	FORMULA	`a(n) = Prod(if n>d^2 then 1 else 1-a(d): d<n and n mod d = 0); a(1)=0.`
	MATHEMATICA	`a[1] = 0; a[n_] := a[n] = Product[ If[ n > d^2, 1, 1-a[d]], {d, Select[ Range[n-1], Mod[n, #] == 0 &] } ]; Table[ a[n], {n, 1, 105}](* From Jean-François Alcover, Feb 15 2012, after formula *)`
	CROSSREFS	`Sequence in context: A100821 A139689 A073070 * A066829 A174207 A048820` `Adjacent sequences: A099101 A099102 A099103 * A099105 A099106 A099107`
	KEYWORD	`nonn,changed`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Sep 26 2004`

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Last modified February 15 07:42 EST 2012. Contains 205717 sequences.