OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..500
Index entries for linear recurrences with constant coefficients, signature (17,-84,108).
FORMULA
G.f.: 1/((1-2*x)*(1-6*x)*(1-9*x)).
From Vincenzo Librandi, Sep 01 2011: (Start)
a(n) = (2^n - 21*6^n + 27*9^n)/7.
a(n) = 17*a(n-1) - 84*a(n-2) + 108*a(n-3) for n > 2.
a(n) = 15*a(n-1) - 54*a(n-2) + 2^n. (End)
MATHEMATICA
CoefficientList[Series[1/((1-2x)(1-6x)(1-9x)), {x, 0, 30}], x] (* or *) LinearRecurrence[{17, -84, 108}, {1, 17, 205}, 30] (* Harvey P. Dale, Jan 19 2019 *)
PROG
(Magma) [(2^n-21*6^n+27*9^n)/7: n in [0..20]]; // Vincenzo Librandi, Sep 01 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved