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 A109214 #11 Sep 01 2025 17:35:27
%S A109214 1,2,2,4,8,32,256,5888,3838976,34109301760,231888097227054080,
%T A109214 1556059601911449331359933440,
%U A109214 125186119679477750610733678211850458005934080,55507466796083630515105997822341552764197877620395801846452095434158080
%N A109214 Product of a(n-1) and digit reversal of a(n-2).
%C A109214 The next term (a(15)) has 115 digits. - _Harvey P. Dale_, Nov 14 2011
%F A109214 a(n) = a(n-1)*R(a(n-2)).
%p A109214 R:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||n):
%p A109214 a:= proc(n) option remember; `if`(n<3, n, a(n-1)*R(a(n-2))) end:
%p A109214 seq(a(n), n=1..14); # _Alois P. Heinz_, Sep 01 2025
%t A109214 a[1]=1;a[2]=2;a[n_]:=a[n]=a[n-1]*FromDigits[Reverse[IntegerDigits[a[n-2]]]]; A109214=Table[a[n], {n, 13}]
%t A109214 Transpose[NestList[{Last[#],Last[#]FromDigits[Reverse[ IntegerDigits[ First[ #]]]]}&,{1,2},13]][[1]] (* _Harvey P. Dale_, Nov 14 2011 *)
%Y A109214 Cf. A000301 (a(n) = a(n-1)*a(n-2)), A004086 (R(n) = digit reversal of n), A109213 (a(n) = a(n-2)*R(a(n-1))).
%K A109214 base,nonn,changed
%O A109214 1,2
%A A109214 _Zak Seidov_, Jun 22 2005
%E A109214 One more term (a(14)) from _Harvey P. Dale_, Nov 14 2011