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 A225987 T(n,k)=Number of pairs of orthogonal (-x,y) vectors of length k*(x+y), where x/y is the n-th rational <= 1, ordered first by y and then x, e.g. 1/1, 1/2, 1/3, 2/3, 1/4, 3/4 ... 19
 4, 48, 9, 640, 390, 20, 8960, 20160, 3192, 60, 129024, 1106424, 652784, 48720, 45, 1892352, 62606544, 134432480, 41801760, 26010, 420, 28114944, 3611217792, 28244153600, 36951200000, 21594300, 8168160, 102, 421724160, 211096262400 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Table starts ..4....48......640........8960.........129024...........1892352 ..9...390....20160.....1106424.......62606544........3611217792 .20..3192...652784...134432480....28244153600.....6052498776192 .60.48720.41801760.36951200000.33792065269760.31520952625612800 .45.26010.21594300.15593341800.11432293516320..8690522384325600 LINKS R. H. Hardin, Table of n, a(n) for n = 1..1056 EXAMPLE Some solutions for n=1 k=4 .-1..1....1..1...-1.-1...-1.-1...-1..1....1..1...-1..1...-1.-1...-1.-1...-1..1 ..1..1...-1.-1...-1..1...-1..1....1..1...-1..1...-1.-1...-1..1...-1..1...-1.-1 .-1..1...-1..1....1..1...-1.-1...-1..1....1.-1....1.-1...-1.-1....1.-1....1.-1 .-1.-1...-1.-1....1.-1...-1.-1....1..1...-1.-1....1.-1...-1..1....1.-1....1.-1 ..1.-1....1.-1...-1.-1....1.-1...-1.-1...-1.-1....1..1...-1..1...-1..1...-1.-1 ..1.-1...-1..1....1..1....1..1...-1..1....1.-1....1.-1...-1.-1...-1.-1...-1.-1 ..1..1....1..1...-1..1....1.-1....1.-1....1.-1....1..1....1..1...-1.-1...-1.-1 ..1..1....1.-1...-1..1...-1..1...-1.-1...-1.-1....1..1....1.-1...-1.-1....1.-1 CROSSREFS Row 1 is A098402. Sequence in context: A334699 A358885 A358889 * A178429 A370417 A242225 Adjacent sequences: A225984 A225985 A225986 * A225988 A225989 A225990 KEYWORD nonn,tabl AUTHOR R. H. Hardin, May 22 2013 STATUS approved

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Last modified August 3 11:33 EDT 2024. Contains 374887 sequences. (Running on oeis4.)