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 A174666 #22 Jul 30 2024 03:10:00
%S A174666 1,3,6,36,432,31104,26873856,1671768834048,89853749822987698176,
%T A174666 300429397152833661135077712592896,
%U A174666 53989415782483456907192461472369228929621535219515392
%N A174666 a(n) = 2 * a(n-2) * a(n-1) with a(1)=1 and a(2)=3.
%H A174666 Vincenzo Librandi, <a href="/A174666/b174666.txt">Table of n, a(n) for n = 1..17</a>
%F A174666 a(n) = 2^A000071(n) * 3^A000045(n-1). - _R. J. Mathar_, Mar 30 2010
%F A174666 a(n) = A166470(n-1)/2. - _Alois P. Heinz_, Sep 16 2022
%t A174666 Nest[Append[#,2Times@@Take[#,-2]]&,{1,3},10] (* _Harvey P. Dale_, Apr 20 2011 *)
%t A174666 RecurrenceTable[{a[1] == 1, a[2] == 3, a[n] == 2 a[n-2] a[n-1]}, a, {n, 12}] (* _Vincenzo Librandi_, Jun 19 2016 *)
%t A174666 nxt[{a_,b_}]:={b,2*a*b}; NestList[nxt,{1,3},10][[;;,1]] (* _Harvey P. Dale_, Apr 08 2023 *)
%o A174666 (Magma) I:=[1,3]; [n le 2 select I[n] else 2*Self(n-2)*Self(n-1): n in [1..11]]; // _Vincenzo Librandi_, Jun 19 2016
%o A174666 (SageMath) [2^(fibonacci(n)-1)*3^fibonacci(n-1) for n in range(1,13)] # _G. C. Greubel_, Jul 30 2024
%Y A174666 Cf. A000045, A000071, A166470.
%K A174666 nonn
%O A174666 1,2
%A A174666 _Giovanni Teofilatto_, Mar 26 2010
%E A174666 Formula replaced by a non-redundant one by _R. J. Mathar_, Mar 30 2010