id:A078594 - OEIS Search Results

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Number of pairs (x,y) 1<=x<=y<=n such that 1/x+1/y+1/n > 1/2.

+0
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1, 3, 6, 10, 15, 20, 24, 26, 29, 30, 33, 34, 36, 37, 38, 40, 42, 43, 45, 46, 48, 50, 52, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 87, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132 (list; graph; listen)

	OFFSET	`1,2`
	FORMULA	`for n>=43 a(n) = 2n-4`
	PROGRAM	`(PARI) a(n)=sum(i=1, n, sum(j=1, i, if(sign(1/i+1/j+1/n-1/2)-1, 0, 1)))`
	CROSSREFS	`Sequence in context: A029716 A162553 A080518 this_sequence A027920 A033438 A037452` `Adjacent sequences: A078591 A078592 A078593 this_sequence A078595 A078596 A078597`
	KEYWORD	`nonn`
	AUTHOR	`Benoit Cloitre (benoit7848c(AT)orange.fr), Dec 08 2002`

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Last modified November 30 13:13 EST 2009. Contains 167758 sequences.

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