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 A248505 #20 Nov 17 2014 22:07:35
%S A248505 3,2,-1,-2,-1,2,3,6,3,18,15,270,255,68850,68595,4722765750,4722697155,
%T A248505 22304192371256441250,22304192366533744095,
%U A248505 497476997228678085728479670747901918750,497476997228678085706175478381368174655
%N A248505 Alternating the subtraction and multiplication of two previous terms, starting with 3, 2.
%F A248505 For n odd a(n) = a(n-1) - a(n-2),
%F A248505 For n even a(n) = a(n-1) * a(n-2),
%F A248505 a(1) = 3, a(2) = 2.
%e A248505 For n = 3, a(n) = a(2) - a(1) = 2 - 3 = -1.
%t A248505 a248505[n_Integer] := Module[{f},
%t A248505 f[1] = 3; f[2] = 2; f[k_] := If[EvenQ[k], f[k - 1] * f[k - 2], f[k - 1] - f[k - 2]]; f /@ Range[n]]; a248505[21] (* _Michael De Vlieger_, Nov 17 2014 *)
%o A248505 (PARI) v=[3,2];for(n=1,20,if(n%2,v=concat(v,v[#v]-v[#v-1]));if(!(n%2),v=concat(v,v[#v]*v[#v-1])));v \\ _Derek Orr_, Oct 29 2014
%Y A248505 Cf. A248479.
%K A248505 sign
%O A248505 1,1
%A A248505 _Stuart E Anderson_, Oct 07 2014
%E A248505 More terms from _Colin Barker_, Oct 07 2014