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%I #12 Feb 01 2022 00:30:05
%S 0,0,0,16,104,608,3480,19212,213280,587072,3237456
%N Number of semi-magic (only short lines are magic) knight's tours on a 4 X 2n board.
%H G. P. Jelliss, <a href="http://www.mayhematics.com/t/mo.htm">Oblong Magic Knight Tours</a>
%H Awani Kumar, <a href="https://arxiv.org/abs/1802.09340">Studies in Tours of Knight on Rectangular Boards</a>, arXiv:1802.09340 [math.GM], 2018.
%F a(n) = A309273(2*n).
%e Example of a 4 X 10 semi-magic knight's tour (only the short lines are magic):
%e +----+----+----+----+----+----+----+----+----+----+
%e | 1 | 38 | 3 | 24 | 5 | 34 | 9 | 26 | 13 | 30 |
%e +----+----+----+----+----+----+----+----+----+----+
%e | 20 | 23 | 18 | 37 | 8 | 25 | 6 | 29 | 10 | 27 |
%e +----+----+----+----+----+----+----+----+----+----+
%e | 39 | 2 | 21 | 4 | 33 | 16 | 35 | 12 | 31 | 14 |
%e +----+----+----+----+----+----+----+----+----+----+
%e | 22 | 19 | 40 | 17 | 36 | 7 | 32 | 15 | 28 | 11 |
%e +----+----+----+----+----+----+----+----+----+----+
%Y Cf. A309273, A309271.
%K nonn,more
%O 1,4
%A _Awani Kumar_, Oct 28 2019
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