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%I #15 May 10 2020 15:06:17
%S 1,3,15,84,494,2988,18411,114950,724845,4606095,29451240,189264672,
%T 1221417360,7910510312,51388786107,334716829674,2185180379179,
%U 14294808917025,93680975707935,614925987859260,4042236129950970
%N a(n) = C(3n,n) - C(3n,n-4).
%F G.f.: (2*g-1)*(2*g^2-2*g+1)/((3*g-1)*(g-1)^4) where g*(1-g)^2 = x. - _Mark van Hoeij_, Nov 09 2011
%t Table[Binomial[3n,n]-Binomial[3n,n-4],{n,0,20}] (* _Harvey P. Dale_, Dec 14 2012 *)
%o (PARI) a(n) = binomial(3*n,n) - binomial(3*n,n-4); \\ _Michel Marcus_, May 10 2020
%Y a(n) = T(3n, n), where T is defined in A026022.
%K nonn
%O 0,2
%A _Clark Kimberling_
%E More terms from _Ralf Stephan_, Jan 09 2005
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