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a(n) = Sum_{i=0..n} binomial(2^n-1, i).
1

%I #10 Mar 07 2020 07:48:17

%S 1,2,7,64,1941,206368,75611761,94790703104,410032402903457,

%T 6209873423645364736,334295041653397160758401,

%U 64833891274601856058512662528,45812224321723327287804258678310401,119028985004291580552833610988687896223744,1145666652669402964793972560725343625287570503681

%N a(n) = Sum_{i=0..n} binomial(2^n-1, i).

%D R. O. Winder, Enumeration of seven-argument threshold functions, IEEE Trans. Electron. Computers, 14 (1965), 315-.

%t Table[Sum[Binomial[2^n-1,i],{i,0,n}],{n,0,20}] (* _Harvey P. Dale_, Apr 11 2012 *)

%K nonn

%O 0,2

%A _N. J. A. Sloane_