A099139 a(n) = (18^n - (-6)^n)/24.

0, 1, 12, 252, 4320, 79056, 1415232, 25520832, 459095040, 8265390336, 148766948352, 2677865536512, 48201216860160, 867624080265216, 15617220384079872, 281110045277601792, 5059980344811847680, 91079649027723165696, 1639433665572357537792, 29509806081862392348672

Offset

0,3

Comments

In general k^(n-1)*A015518(n) is given by ((3k)^n-(-k)^n)/(4k) with g.f. x/((1+kx)(1-3kx)).

Links

Table of n, a(n) for n=0..19.

Index entries for linear recurrences with constant coefficients, signature (12,108).

Formula

G.f.: x/((1+6x)*(1-18x)).

a(n) = 12a(n-1)+108a(n-2). a(n) = 6^(n-1)*A015518(n).

Mathematica

LinearRecurrence[{12, 108}, {0, 1}, 20] (* Harvey P. Dale, May 24 2015 *)

Crossrefs

Cf. A053524, A053535, A053536, A053537.

Sequence in context: A265453 A367737 A210484 * A289565 A198475 A035013

Adjacent sequences: A099136 A099137 A099138 * A099140 A099141 A099142

Keyword

easy,nonn

Author

Paul Barry, Sep 29 2004

Status

approved