A089683 a(n) = 3^(4*n).

81, 6561, 531441, 43046721, 3486784401, 282429536481, 22876792454961, 1853020188851841, 150094635296999121, 12157665459056928801, 984770902183611232881, 79766443076872509863361, 6461081889226673298932241, 523347633027360537213511521, 42391158275216203514294433201

Offset: 1

Author

Douglas Winston (douglas.winston(AT)srupc.com), Jan 05 2004

Keywords

• nonn
• easy

Links

• Tanya Khovanova, Recursive Sequences.
• Index entries for linear recurrences with constant coefficients, signature (81).

Crossrefs

Cf. A000244, A001019, A008586, A009971.

Programs

Mathematica

3^(4*Range[20]) (* or *) NestList[81#&,81,20] (* Harvey P. Dale, Apr 09 2012 *)

PARI

my(x='x+O('x^16)); Vec(-81*x/(81*x-1)) \\ Elmo R. Oliveira, Jul 09 2025

Formula

a(n) = 81^n.

G.f.: 81*x/(1-81*x). - Philippe Deléham, Nov 25 2008

From Elmo R. Oliveira, Jul 09 2025: (Start)

E.g.f.: exp(81*x) - 1.

a(n) = 81*a(n-1) for n > 1.

a(n) = A001019(n)^2 = A000244(A008586(n)). (End)

Extensions

More terms from Harvey P. Dale, Apr 09 2012