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a(n) = ceiling(log_2(n)*2^n/n).
3

%I #12 Jun 15 2018 20:50:54

%S 0,2,5,8,15,28,52,96,181,341,645,1224,2332,4456,8535,16384,31515,

%T 60729,117218,226594,438637,850192,1649843,3205122,6232879,12132353,

%U 23636674,46088019,89934783,175624456,343195341,671088640,1313061078,2570645474,5035452071

%N a(n) = ceiling(log_2(n)*2^n/n).

%H Harry J. Smith, <a href="/A065618/b065618.txt">Table of n, a(n) for n = 1..200</a>

%o (PARI) { default(realprecision, 100); t=1/log(2); for (n=1, 200, write("b065618.txt", n, " ", ceil( t*log(n)*2^n/n - 0.0000001)) ) } \\ _Harry J. Smith_, Oct 24 2009

%K nonn

%O 1,2

%A _N. J. A. Sloane_, Dec 03 2001

%E a(4) corrected and a(34) added by _Harry J. Smith_, Oct 24 2009