id:A157001 - OEIS Search Results

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Fractions x/y, with 1<=x,y<=n, that reduce to (odd)/(even).

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0, 1, 2, 5, 7, 11, 14, 21, 25, 32, 37, 47, 53, 63, 70, 85, 93, 106, 115, 132, 142, 158, 169, 191, 203, 222, 235, 259, 273, 295, 310, 341, 357, 382, 399, 430, 448, 476, 495, 532, 552, 583, 604, 642, 664, 698, 721, 767, 791, 828, 853, 898, 924, 964, 991, 1043, 1071 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`Equivalently, a(n) is the number of fractions x/y, with 1<=x,y<=n, that reduce to (even)/(odd).`
	CROSSREFS	`a(n)=(n^2-A135013)/2` `Sequence in context: A099835 A133436 A001225 this_sequence A134640 A032616 A006066` `Adjacent sequences: A156998 A156999 A157000 this_sequence A157002 A157003 A157004`
	KEYWORD	`nonn`
	AUTHOR	`Adam McDougall (mcdougall.adam(AT)gmail.com), Feb 20 2009`

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Last modified December 19 12:50 EST 2009. Contains 171053 sequences.

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