A170833 a(n) = 4^(floor(n/2))+4^(floor(n/2)-1)-4^(floor((n-1)/3)).

4, 4, 16, 16, 76, 64, 304, 304, 1216, 1216, 5056, 4864, 20224, 20224, 80896, 80896, 326656, 323584, 1306624, 1306624, 5226496, 5226496, 20955136, 20905984, 83820544, 83820544, 335282176, 335282176, 1341915136, 1341128704, 5367660544, 5367660544, 21470642176

Offset

2,1

Links

Table of n, a(n) for n=2..34.

R. P. Stanley, Problem 11348, Amer. Math. Monthly, 117 (2010), 87-88.

Index entries for linear recurrences with constant coefficients, signature (0,4,4,0,-16).

Formula

a(n) = 4*a(n-2)+4*a(n-3)-16*a(n-5). G.f.: -4*x^2*(x^4+4*x^3-x-1) / ((2*x-1)*(2*x+1)*(4*x^3-1)). - Colin Barker, Jul 26 2013

Mathematica

LinearRecurrence[{0, 4, 4, 0, -16}, {4, 4, 16, 16, 76}, 40] (* Harvey P. Dale, Mar 11 2017 *)

Crossrefs

Cf. A170831, A170832, A170834.

Sequence in context: A164906 A213173 A222956 * A231940 A129884 A137725

Adjacent sequences: A170830 A170831 A170832 * A170834 A170835 A170836

Keyword

nonn,easy

Author

N. J. A. Sloane, Dec 30 2009

Status

approved