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%I #13 Sep 24 2020 04:09:41
%S 1,4,5,16,20,25,64,80,100,125,256,320,400,500,625,1024,1280,1600,2000,
%T 2500,3125,4096,5120,6400,8000,10000,12500,15625,16384,20480,25600,
%U 32000,40000,50000,62500,65536,78125,81920,102400,128000,160000,200000,250000
%N Numbers of form 4^i*5^j, with i, j >= 0.
%H Amiram Eldar, <a href="/A025617/b025617.txt">Table of n, a(n) for n = 1..10000</a>
%F Sum_{n>=1} 1/a(n) = (4*5)/((4-1)*(5-1)) = 5/3. - _Amiram Eldar_, Sep 24 2020
%F a(n) ~ exp(sqrt(2*log(4)*log(5)*n)) / sqrt(20). - _Vaclav Kotesovec_, Sep 24 2020
%t n = 10^5; Flatten[Table[4^i*5^j, {i, 0, Log[4, n]}, {j, 0, Log[5, n/4^i]}]] // Sort (* _Amiram Eldar_, Sep 24 2020 *)
%Y Subsequence of A003592.
%K easy,nonn
%O 1,2
%A _David W. Wilson_
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