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 A091788 #12 Aug 15 2017 03:07:08 %S A091788 1,2,2,4,16,96,5184,829440,1911029760,13002646487040, %T A091788 10065920762063093760,9319918463639717615448883200, %U A091788 137422208150223932126848386360776224407552000 %N A091788 a(1) = 1, a(2) = 2 and a(n) = product of the nonzero digits of all previous terms. %H A091788 <a href="/index/Coi#Colombian">Index entries for Colombian or self numbers and related sequences</a> %F A091788 a(n) = a(n-1)*product of nonzero digits of a(n-1) (n >= 4). - _Emeric Deutsch_, Apr 15 2005 %p A091788 p:=proc(n) local pr,nn,j: pr:=1: nn:=convert(n,base,10): for j from 1 to nops(nn) do if nn[j]>0 then pr:=pr*nn[j] else pr:=pr: fi: od: end: a:=proc(n) if n=1 then 1 elif n=2 then 2 elif n=3 then 2 else a(n-1)*p(a(n-1)) fi end: seq(a(n),n=1..14); # p(n) is the product of the nonzero digits of n # _Emeric Deutsch_, Apr 15 2005 %Y A091788 Cf. A051801, A230101. %K A091788 base,nonn %O A091788 1,2 %A A091788 _Amarnath Murthy_, Feb 18 2004 %E A091788 More terms from _Emeric Deutsch_, Apr 15 2005