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%I #11 Jan 23 2025 10:24:05
%S 1,38,17370,31532760,152770174200,1623335272297200,
%T 33237789624004165200,1195230914866984819824000,
%U 70405077040237339921593072000,6434319990707289925222982683680000,873465373058505314477955434719930080000
%N Number of games that can be played with a set of 4n cards.
%H J.-P. Delahaye and P. Mathieu, <a href="https://www.cristal.univ-lille.fr/~jdelahay/pls/1995/030.pdf">La bataille, enfin analysée</a>, in Pour la Science, pp. 101 No. 215 September 1995 Paris.
%F a(n) = {(4n)!/(4!)^n + (2n)!/(2!)^n}/2.
%o (PARI) a(n) = ((4*n)!/24^n + (2*n)!/2^n)/2 \\ _Charles R Greathouse IV_, Sep 06 2016
%K fini,full,nonn,easy
%O 1,2
%A _Lekraj Beedassy_, Sep 03 2005