%I #16 May 11 2014 18:01:48
%S 1,4,8,16,16,32,32,64,64,64,64,128,128,128,128,256,256,256,256,256,
%T 256,256,512,512,512,512,512,512,512,512,512,1024,1024,1024,1024,1024,
%U 1024,1024,1024,1024,1024,1024,1024,1024,1024,2048,2048,2048,2048,2048,2048
%N Largest power of 2 <= n^2.
%C The first values of n that produce powers of 4 are precisely the powers of 2.
%e a(3) = 8 because 3^2 = 9 and the largest power of 2 <= 9 is 8.
%o (PARI) a(n)=2^(#binary(n^2)1) \\ _Charles R Greathouse IV_, May 11 2014
%K nonn,easy
%O 1,2
%A _J. Lowell_, May 11 2014
