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a(n) = (18*n)!*(2*n)!/((9*n)!*(6*n)!*(5*n)!).
2

%I #7 Nov 28 2017 11:49:18

%S 1,408408,802241960520,1823169705017624880,4396944340992842923469640,

%T 10954213672604884898541157653408,

%U 27856219773497860095974794307896603536,71846723613356502547294848257330357588794200,187234481335648875117449455455153824826269008835400

%N a(n) = (18*n)!*(2*n)!/((9*n)!*(6*n)!*(5*n)!).

%F G.f.: hypergeom([1/18, 5/18, 7/18, 1/2, 11/18, 13/18, 17/18], [1/5, 1/3, 2/5, 3/5, 2/3, 4/5], 8707129344/3125*x).

%Y Cf. A295431.

%K nonn

%O 0,2

%A _Gheorghe Coserea_, Nov 27 2017