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 A060963 Number of pairings of the first 2n positive integers so that the absolute differences of each pair are different. 9
 1, 1, 1, 5, 29, 145, 957, 8397, 85169, 944221, 11639417, 160699437, 2430145085, 39776366397, 703161838717, 13369111112753 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS Number of perfect Skolem-type sequences. LINKS G. Nordh, Perfect Skolem sequences, arXiv:math/0506155 [math.CO], 2005. EXAMPLE a(3)=5 since the 5 pairings of {1, 2, 3, 4, 5, 6} are {1, 3} {2, 6} {4, 5}, {1, 5} {2, 3} {4, 6}, {1, 5} {2, 4} {3, 6}, {1, 4} {2, 6} {3, 5}, {1, 6} {2, 5} {3, 4}. CROSSREFS Cf. A261516, A261517. Sequence in context: A163082 A189430 A273078 * A107002 A027864 A272839 Adjacent sequences:  A060960 A060961 A060962 * A060964 A060965 A060966 KEYWORD nonn AUTHOR Erich Friedman, May 08 2001 EXTENSIONS Offset corrected by Alois P. Heinz, Sep 14 2015 a(14) from Fausto A. C. Cariboni, Mar 03 2017 a(15) from Fausto A. C. Cariboni, Apr 10 2017 STATUS approved

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Last modified December 8 18:37 EST 2019. Contains 329865 sequences. (Running on oeis4.)