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From Philippe Deléham, Jul 11 2005: (Start)
Binomial transform of A081342.
6th binomial transform of (1, 0, 9, 0, 81, 0, 729, 0, . . ).
Inverse binomial transform of A081343.
a(n) = 12*a(n-1) - 27*a(n-2), a(0) = 1, a(1) = 6.
G.f.: (1-6*x)/((1-3*x)*(1-9*x)).
E.g.f.: exp(7*x)*cosh(3*x). (End)
a(n) = ((6+sqrt(9))^n+(6-sqrt(9))^n)/2 [Al Hakanson (hawkuu(AT)gmail.com), Dec 08 2008]
a(n) = sum(k=1..3^n, k ). [Joerg Arndt, Sep 01 2013]
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