This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A025624 #24 Jul 06 2025 10:03:00
%S A025624 1,5,9,25,45,81,125,225,405,625,729,1125,2025,3125,3645,5625,6561,
%T A025624 10125,15625,18225,28125,32805,50625,59049,78125,91125,140625,164025,
%U A025624 253125,295245,390625,455625,531441,703125,820125,1265625,1476225,1953125
%N A025624 Numbers of form 5^i*9^j, with i, j >= 0.
%H A025624 Amiram Eldar, <a href="/A025624/b025624.txt">Table of n, a(n) for n = 1..10000</a>
%F A025624 Sum_{n>=1} 1/a(n) = (5*9)/((5-1)*(9-1)) = 45/32. - _Amiram Eldar_, Sep 24 2020
%F A025624 a(n) ~ exp(sqrt(2*log(5)*log(9)*n)) / sqrt(45). - _Vaclav Kotesovec_, Sep 24 2020
%F A025624 a(n) = 5^A025654(n) * 9^A025679(n). - _R. J. Mathar_, Jul 06 2025
%t A025624 f[upto_]:=Module[{maxi=Ceiling[Log[5,upto]],maxj=Ceiling[Log[9,upto]],s}, s=Union[Flatten[Outer[Times,5^Range[0,maxi], 9^Range[0,maxj]]]]; Select[s,#<=upto&]]; f[2000000] (* _Harvey P. Dale_, Mar 27 2011 *)
%Y A025624 Subsequence of A003593.
%K A025624 easy,nonn
%O A025624 1,2
%A A025624 _David W. Wilson_