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A091788 a(1) = 1, a(2) = 2 and a(n) = product of the nonzero digits of all previous terms. 0

%I

%S 1,2,2,4,16,96,5184,829440,1911029760,13002646487040,

%T 10065920762063093760,9319918463639717615448883200,

%U 137422208150223932126848386360776224407552000

%N a(1) = 1, a(2) = 2 and a(n) = product of the nonzero digits of all previous terms.

%H <a href="/index/Coi#Colombian">Index entries for Colombian or self numbers and related sequences</a>

%F a(n) = a(n-1)*product of nonzero digits of a(n-1) (n >= 4). - _Emeric Deutsch_, Apr 15 2005

%p 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 Cf. A051801, A230101.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Feb 18 2004

%E More terms from _Emeric Deutsch_, Apr 15 2005

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Last modified August 7 11:34 EDT 2020. Contains 336275 sequences. (Running on oeis4.)