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A182467
a(n) = 3a(n-1) - 2a(n-2) with a(0)=36 and a(1)=90.
7
36, 90, 198, 414, 846, 1710, 3438, 6894, 13806, 27630, 55278, 110574, 221166, 442350, 884718, 1769454, 3538926, 7077870, 14155758, 28311534, 56623086, 113246190, 226492398, 452984814, 905969646, 1811939310, 3623878638, 7247757294, 14495514606, 28991029230
OFFSET
0,1
COMMENTS
Number of vertices into building blocks of 3d objects with 9 vertices.
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 *)
KEYWORD
nonn,easy
AUTHOR
Odimar Fabeny, Apr 30 2012
STATUS
approved