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A166035
a(n) = (3^n+6*(-4)^n)/7.
7
1, -3, 15, -51, 231, -843, 3615, -13731, 57111, -221883, 907215, -3569811, 14456391, -57294123, 230770815, -918300291, 3687550071, -14707153563, 58957754415, -235443597171, 942936650151, -3768259816203, 15083499618015
OFFSET
0,2
FORMULA
a(n) = -a(n-1) + 12*a(n-2), a(0) = 1, a(1) = -3, for n>1.
a(n) = Sum_{0<=k<=n} A112555(n,k)*(-4)^k.
G.f.: (1-2x)/(1+x-12x^2).
E.g.f.: (1/7)*(exp(3*x) + 6*exp(-4*x)). - G. C. Greubel, Apr 24 2016
MATHEMATICA
LinearRecurrence[{-1, 12}, {1, -3}, 100] (* G. C. Greubel, Apr 24 2016 *)
PROG
(PARI) a(n)= (3^n+6*(-4)^n)/7;
for(n=0, 33, print1(a(n), ", "));
CROSSREFS
Sequence in context: A284663 A231747 A192742 * A038192 A212869 A371481
KEYWORD
easy,sign
AUTHOR
Philippe Deléham, Oct 05 2009
EXTENSIONS
a(5) corrected by Tilman Neumann, Dec 31 2010
STATUS
approved