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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, 271734091323897
OFFSET
0,4
COMMENTS
Number of perfect Skolem-type sequences.
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
KEYWORD
nonn,more
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
a(16) from Edward Moody, Feb 17 2020
STATUS
approved