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 A175138 #11 Sep 02 2025 01:54:10
%S A175138 3,5,15,225,50625,2562890625,6568408355712890625,
%T A175138 43143988327398919500410556793212890625,
%U A175138 1861403728794734215467410604755702820123364205073812627233564853668212890625
%N A175138 a(n) = Product_{i=1..n-1} a(i), with a(1) = 3 and a(2) = 5.
%C A175138 Except for first three terms, a(n) = (a(n-1))^2.
%F A175138 a(n) = 15^(2^(n-3)), n > 2.
%t A175138 Join[{3,5},NestList[#^2&,15,7]] (* _Harvey P. Dale_, Feb 08 2013 *)
%K A175138 nonn,easy,changed
%O A175138 1,1
%A A175138 _Giovanni Teofilatto_, Feb 23 2010
%E A175138 Edited by _Jaroslav Krizek_ and _R. J. Mathar_, Mar 04 2010