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

1, 2, 2, 4, 16, 96, 5184, 829440, 1911029760, 13002646487040, 10065920762063093760, 9319918463639717615448883200, 137422208150223932126848386360776224407552000

Offset

1,2

Links

Table of n, a(n) for n=1..13.

Index entries for Colombian or self numbers and related sequences

Formula

a(n) = a(n-1)*product of nonzero digits of a(n-1) (n >= 4). - Emeric Deutsch, Apr 15 2005

Maple

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

Crossrefs

Cf. A051801, A230101.

Sequence in context: A244108 A032318 A090753 * A063401 A168088 A168089

Adjacent sequences: A091785 A091786 A091787 * A091789 A091790 A091791

Keyword

base,nonn

Author

Amarnath Murthy, Feb 18 2004

Extensions

More terms from Emeric Deutsch, Apr 15 2005

Status

approved