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a(n) = denominator(n!/4^n).
1

%I #8 Jul 05 2024 14:28:30

%S 1,4,8,32,32,128,256,1024,512,2048,4096,16384,16384,65536,131072,

%T 524288,131072,524288,1048576,4194304,4194304,16777216,33554432,

%U 134217728,67108864,268435456,536870912,2147483648,2147483648,8589934592,17179869184,68719476736

%N a(n) = denominator(n!/4^n).

%F a(n) = denominator((1/(2*Pi))*int(exp(i*4*t)(-((Pi-t)/i)^n),t,0,2*Pi)), i=sqrt(-1).

%F a(n) = 2^A092391(n).

%t Table[Denominator[n!/4^n],{n,0,30}] (* _Harvey P. Dale_, Mar 05 2013 *)

%Y Cf. A049606, A092391.

%K easy,nonn

%O 0,2

%A _Paul Barry_, Apr 02 2007