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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
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OFFSET
0,4
COMMENTS
Number of perfect Skolem-type sequences.
LINKS
Table of n, a(n) for n=0..16.
Edward Moody,
Java program for calculating entries in this sequence and A322178
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
,
A322178
.
Sequence in context:
A163082
A189430
A273078
*
A107002
A339957
A027864
Adjacent sequences:
A060960
A060961
A060962
*
A060964
A060965
A060966
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
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Last modified September 9 10:46 EDT 2024. Contains 375764 sequences. (Running on oeis4.)