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 A372509 #10 Apr 26 2025 20:27:48
%S A372509 1,3,9,15,27,45,81,105,135,225,243,315,405,675,729,945,1215,1575,2025,
%T A372509 2187,2835,3375,3645,4725,6075,6561,8505,10125,10395,10935,11025,
%U A372509 14175,18225,19683,23625,25515,30375,31185,32805,33075,42525,50625
%N A372509 Numbers that can be written as a product of double factorials of odd numbers.
%t A372509 kmax = 60000;
%t A372509 maxExponent = 10;
%t A372509 ff = Select[TakeWhile[Range[3, kmax], #!! < kmax &]!!, OddQ];
%t A372509 lg = Length@ff;
%t A372509 iter = Sequence @@ Table[{x[i], 0, maxExponent}, {i, 1, lg}];
%t A372509 seq = Table[k = Times @@ Table[ff[[i]]^x[i] , {i, 1, lg}]; If[k <= kmax, k, Nothing], Evaluate@iter] // Flatten // Union (* _Jean-François Alcover_, May 11 2024 *)
%Y A372509 Cf. A001013, A001147, A025487, A057863.
%K A372509 nonn
%O A372509 1,2
%A A372509 _Ilya Gutkovskiy_, May 04 2024