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%I M4318 #15 Jan 31 2022 01:20:35
%S 1,1,6,5972,1225533120
%N Number of symmetric Latin squares of order 2n with constant diagonal.
%D N. T. Gridgeman, Latin squares under restriction and a jumboization, J. Rec. Math., 5 (No. 3, 1972), 198-202.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H <a href="/index/La#Latin">Index entries for sequences related to Latin squares and rectangles</a>
%K nonn,hard,nice
%O 1,3
%A _N. J. A. Sloane_
%E Daniele Degiorgi (degiorgi(AT)inf.ethz.ch) suggests that this is an erroneous version of A000438.