A165314 a(0)=1, a(1)=6, a(n)=13*a(n-1)-36*a(n-2) for n>1.

1, 6, 42, 330, 2778, 24234, 215034, 1923018, 17258010, 155125482, 1395342906, 12554940426, 112981880922, 1016786596650, 9150878043258, 82357097082954, 741210652521114, 6670882987788138, 60037895350485690, 540340851995941002

Offset: 0

Author

Philippe Deléham, Sep 14 2009

Keywords

• nonn

Comments

a(n)/a(n-1) tends to 9.

Formula

G.f.: (1-7x)/(1-13x+36x^2). a(n)=Sum_{k, 0<=k<=n}A165253(n,k)*6^(n-k).

a(n) = (2*9^n+3*4^n)/5. [From Klaus Brockhaus, Sep 26 2009]