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%I #8 Dec 05 2024 19:19:16
%S 3,5,21,45,385,819,3465,7293,122265,255255,1062347,2204475,18253053,
%T 37702175,155451825,319929885,10518906825,21585857535,88482569175,
%U 181144476975,1481850184815,3027700543725,12361581411855,25214881603275,411156946959525,837470267650107
%N a(n) = denominator((4^(2*n+1)*n!^2)/((2*n+3)*(2*n)!)).
%p a := n -> (4^(2*n+1)*n!^2)/((2*n+3)*(2*n)!); seq(denom(a(n)), n = 0..25);
%t Table[Denominator[(4^(2*n + 1)*n!^2)/((2*n + 3)*(2*n)!)], {n, 0, 25}] (* _Michael De Vlieger_, Dec 05 2024 *)
%o (PARI) a(n) = denominator((4^(2*n+1)*n!^2)/((2*n+3)*(2*n)!)); \\ _Michel Marcus_, Dec 05 2024
%Y Cf. A102557 (numerator).
%K nonn,frac,new
%O 0,1
%A _Peter Luschny_, Dec 05 2024