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A170831 a(n) = 2^(floor(n/2))+2^(floor(n/2)-1)-2^(floor((n-1)/3)). 3
2, 2, 4, 4, 10, 8, 20, 20, 40, 40, 88, 80, 176, 176, 352, 352, 736, 704, 1472, 1472, 2944, 2944, 6016, 5888, 12032, 12032, 24064, 24064, 48640, 48128, 97280, 97280, 194560, 194560, 391168, 389120, 782336, 782336, 1564672, 1564672, 3137536, 3129344, 6275072 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Table of n, a(n) for n=2..44.

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

Index entries for linear recurrences with constant coefficients, signature (0,2,2,0,-4).

FORMULA

a(n) = 2*a(n-2)+2*a(n-3)-4*a(n-5). G.f.: -2*x^2*(x^4+2*x^3-x-1) / ((2*x^2-1)*(2*x^3-1)). - Colin Barker, Jul 25 2013

CROSSREFS

Cf. A170832, A170833, A170834.

Sequence in context: A318838 A231523 A114338 * A133406 A240381 A295746

Adjacent sequences:  A170828 A170829 A170830 * A170832 A170833 A170834

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Dec 30 2009

STATUS

approved

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Last modified September 16 23:53 EDT 2021. Contains 347477 sequences. (Running on oeis4.)