A166927 a(n) = 20*a(n-1) - 64*a(n-2) for n > 1; a(0) = 1, a(1) = 18.

1, 18, 296, 4768, 76416, 1223168, 19572736, 313171968, 5010784256, 80172679168, 1282763390976, 20524216352768, 328387470032896, 5254199554080768, 84067192999510016, 1345075088529031168, 21521201418611982336

Offset: 0

Author

Klaus Brockhaus, Oct 23 2009

Keywords

• nonn

Comments

lim_{n -> infinity} a(n)/a(n-1) = 16.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..200
• Index entries for linear recurrences with constant coefficients, signature (20, -64).

Crossrefs

Cf. A166914, A166917.

Programs

Magma

[ n le 2 select 17*n-16 else 20*Self(n-1)-64*Self(n-2): n in [1..17] ];

Mathematica

LinearRecurrence[{20, -64}, {1, 18}, 50] (* G. C. Greubel, May 28 2016 *)

Formula

a(n) = (7*16^n - 4^n)/6.

G.f.: (1 - 2*x)/((1-4*x)*(1-16*x)).

E.g.f.: (1/6)*(7*exp(16*x) - exp(4*x)). - G. C. Greubel, May 28 2016