OFFSET
0,1
COMMENTS
Number of vertices into building blocks of 3d objects with 9 vertices.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3, -2).
FORMULA
a(n) = a(n-1)*2 + 18
G.f.: -((18*(x-2))/(2*x^2-3*x+1)). - Harvey P. Dale, Apr 29 2013
a(n) = 18*A153893(n). - Michel Marcus, Jun 01 2014
EXAMPLE
a(0) = 9+18+9;
a(1) = 9+18+36+18+9;
a(2) = 9+18+36+72+36+18+9;
a(3) = 9+18+36+72+144+72+36+18+9.
MATHEMATICA
LinearRecurrence[{3, -2}, {36, 90}, 30] (* or *) CoefficientList[Series[(-18(x-2))/(1-3x+2x^2), {x, 0, 30}], x] (* Harvey P. Dale, Apr 29 2013 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Odimar Fabeny, Apr 30 2012
STATUS
approved