The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A157001 Fractions x/y, with 1<=x,y<=n, that reduce to (odd)/(even). 0
 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; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Equivalently, a(n) is the number of fractions x/y, with 1<=x,y<=n, that reduce to (even)/(odd). LINKS CROSSREFS a(n)=(n^2-A135013)/2 Sequence in context: A191175 A191125 A001225 * A134640 A216094 A184857 Adjacent sequences:  A156998 A156999 A157000 * A157002 A157003 A157004 KEYWORD nonn AUTHOR Adam McDougall (mcdougall.adam(AT)gmail.com), Feb 20 2009 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 27 08:22 EDT 2021. Contains 347689 sequences. (Running on oeis4.)