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%I #21 Sep 24 2020 03:42:20
%S 1,2,4,8,9,16,18,32,36,64,72,81,128,144,162,256,288,324,512,576,648,
%T 729,1024,1152,1296,1458,2048,2304,2592,2916,4096,4608,5184,5832,6561,
%U 8192,9216,10368,11664,13122,16384,18432,20736,23328,26244,32768,36864,41472
%N Numbers of form 2^i*9^j, with i, j >= 0.
%H Robert Israel, <a href="/A025611/b025611.txt">Table of n, a(n) for n = 1..10000</a>
%F Sum_{n>=1} 1/a(n) = (2*9)/((2-1)*(9-1)) = 9/4. - _Amiram Eldar_, Sep 24 2020
%F a(n) ~ exp(sqrt(2*log(2)*log(9)*n)) / sqrt(18). - _Vaclav Kotesovec_, Sep 24 2020
%p N:= 10^5: # for terms <= N
%p sort([seq(seq(2^i*9^j,i=0..ilog2(N/9^j)),j=0..floor(log[9](N)))]); # _Robert Israel_, Mar 23 2020
%t Take[Union[2^First[#] 9^Last[#]&/@Tuples[Range[0,20],{2}]],50] (* _Harvey P. Dale_, May 26 2011 *)
%t n = 10^5; Flatten[Table[2^i*9^j, {i, 0, Log[2, n]}, {j, 0, Log[9, n/2^i]}]] // Sort (* _Amiram Eldar_, Sep 24 2020 *)
%Y Subsequence of A003586.
%K easy,nonn
%O 1,2
%A _David W. Wilson_
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