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A131174 a(2n) = 2*A000217(n), a(2n+1) = A000217(n). 1
0, 0, 2, 1, 6, 3, 12, 6, 20, 10, 30, 15, 42, 21, 56, 28, 72, 36, 90, 45, 110, 55, 132, 66, 156, 78, 182, 91, 210, 105, 240, 120, 272, 136, 306, 153, 342, 171, 380, 190, 420, 210, 462, 231, 506, 253, 552, 276, 600, 300, 650, 325, 702, 351, 756, 378, 812, 406, 870, 435 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (0, 3, 0, -3, 0, 1).

FORMULA

a(n) = 3*a(n-2)-3*a(n-4)+a(n-6).

G.f.: x^2*(2+x)/((1-x)^3*(1+x)^3). [R. J. Mathar, Jul 17 2009]

a(n) = (3*n^2+4*n-1+(n^2+4*n+1)*(-1)^n)/16. - Luce ETIENNE, Aug 19 2014

MAPLE

A000217 := proc(n) n*(n+1)/2 ; end: A131174 := proc(n) if n mod 2 = 0 then 2*A000217(n/2) ; else A000217((n-1)/2) ; fi ; end: seq(A131174(n), n=0..90) ; # R. J. Mathar, Oct 26 2007

MATHEMATICA

LinearRecurrence[{0, 3, 0, -3, 0, 1}, {0, 0, 2, 1, 6, 3}, 60] (* Harvey P. Dale, Jun 01 2012 *)

CROSSREFS

Sequence in context: A050137 A086111 A262603 * A291539 A135994 A217646

Adjacent sequences:  A131171 A131172 A131173 * A131175 A131176 A131177

KEYWORD

nonn

AUTHOR

Paul Curtz, Sep 24 2007

EXTENSIONS

Edited by N. J. A. Sloane, Sep 27 2007

More terms from R. J. Mathar, Oct 26 2007

STATUS

approved

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Last modified August 11 06:25 EDT 2020. Contains 336422 sequences. (Running on oeis4.)