A009971 Powers of 27.

1, 27, 729, 19683, 531441, 14348907, 387420489, 10460353203, 282429536481, 7625597484987, 205891132094649, 5559060566555523, 150094635296999121, 4052555153018976267, 109418989131512359209, 2954312706550833698643, 79766443076872509863361, 2153693963075557766310747

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

Same as Pisot sequences E(1, 27), L(1, 27), P(1, 27), T(1, 27). Essentially same as Pisot sequences E(27, 729), L(27, 729), P(27, 729), T(27, 729). See A008776 for definitions of Pisot sequences.

The compositions of n in which each natural number is colored by one of p different colors are called p-colored compositions of n. For n >= 1, a(n) equals the number of 27-colored compositions of n such that no adjacent parts have the same color. - Milan Janjic, Nov 17 2011

Links

• T. D. Noe, Table of n, a(n) for n = 0..100
• Tanya Khovanova, Recursive Sequences.
• Index entries for linear recurrences with constant coefficients, signature (27).

Crossrefs

Cf. A000244, A001019, A008585, A008776.

Programs

Magma

[27^n: n in [0..100]]; // Vincenzo Librandi, Nov 21 2010

Mathematica

27^Range[0, 20] (* Paolo Xausa, Jul 19 2024 *)

PARI

a(n)=27^n \\ Charles R Greathouse IV, Sep 24 2015

Sage

[lucas_number1(n,27,0) for n in range(1, 17)] # Zerinvary Lajos, Apr 29 2009

Formula

G.f.: 1/(1-27*x). - Philippe Deléham, Nov 24 2008

a(n) = 27^n; a(n) = 27*a(n-1), n > 0; a(0)=1. - Vincenzo Librandi, Nov 21 2010

From Elmo R. Oliveira, Jul 10 2025: (Start)

E.g.f.: exp(27*x).

a(n) = A000244(n)*A001019(n) = A000244(A008585(n)). (End)