0,3

Table of n, a(n) for n=0..98.

a(n) = 3+3*(-1)^n-6*[C(2*n,n) mod 2], with n>=0. [Paolo P. Lava, Sep 23 2009]

G.f.: 6*x^2/(1 - x^2). - Chai Wah Wu, Jun 21 2016

Sequence in context: A217221 A158090 A010677 * A303494 A198368 A064373

Adjacent sequences: A021166 A021167 A021168 * A021170 A021171 A021172

nonn,cons

N. J. A. Sloane.

approved