id:A034806 - OEIS Search Results

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Number of unique sets of 2 numbers > 1 such that their product is between x^2 and (x+1)^2.

+0
2

2, 5, 9, 12, 17, 22, 28, 32, 40, 41, 50, 56, 63, 68, 78, 80, 91, 94, 102, 110, 120, 123, 131, 141, 148, 156, 166, 163, 179, 185, 195, 206, 214, 211, 229, 237, 248, 248, 265, 260, 281, 284, 296, 305, 314, 320, 333, 337 (list; graph; listen)

	OFFSET	`2,1`
	FORMULA	`sum(floor( (2x+(x^2)%k)/k), for k=2..x).`
	EXAMPLE	`a(3)=5 because the only sets of 2-numbers > 1 that form a product between 3^2 and 4^2 are (2,5) (2,6) (3,4) (2,7) (3,5).`
	CROSSREFS	`Cf. A037048, A037092.` `Sequence in context: A086814 A086343 A056549 this_sequence A034307 A070828 A112988` `Adjacent sequences: A034803 A034804 A034805 this_sequence A034807 A034808 A034809`
	KEYWORD	`nonn`
	AUTHOR	`Joe K. Crump (joecr(AT)carolina.rr.com)`

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Last modified December 2 11:54 EST 2009. Contains 167921 sequences.

AT&T Labs Research