A133642 a(n) = 4*a(n-1)+20*a(n-2) for n>=3, a(0)=1, a(1)=4, a(2)=32.

1, 4, 32, 208, 1472, 10048, 69632, 479488, 3310592, 22832128, 157540352, 1086803968, 7498022912, 51728171008, 356873142272, 2462055989248, 16985686802432, 117183866994688, 808449204027392, 5577474156003328, 38478880704561152, 265465005938311168

Offset

0,2

Links

Table of n, a(n) for n=0..21.

Index entries for linear recurrences with constant coefficients, signature (4,20).

Formula

G.f.: (1-4*x^2)/(1-4*x-20*x^2).

a(n) = Sum_{k=0..n} A122950(n,k)*4^k.

Crossrefs

Cf. A122950.

Sequence in context: A002012 A240408 A248216 * A098981 A120917 A305518

Adjacent sequences: A133639 A133640 A133641 * A133643 A133644 A133645

Keyword

easy,nonn

Author

Philippe Deléham, Dec 31 2007

Extensions

a(15) corrected by Georg Fischer, Mar 13 2020

Status

approved