



1, 3, 8, 21, 54, 136, 337, 825, 2000, 4809, 11484, 27264, 64401, 151455, 354808, 828349, 1927986, 4475080, 10361441, 23936565, 55183904, 126983569, 291698040, 669004352, 1532095329, 3503889147, 8003207912, 18258464741, 41608726254, 94722900936, 215428701233
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OFFSET

0,2


LINKS

Clark Kimberling, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (4, 4, 2, 4, 0, 1)


FORMULA

G.f.: ((1 + x + x^3)/(1 + 2 x + x^3)^2).
a(n) = 4*a(n1)  4*a(n2) + 2*a(n3)  4*a(n4)  a(n6) for n >= 7.


MATHEMATICA

z = 60; s = x/(x  x^3); p = (1  2 s)^2;
Drop[CoefficientList[Series[s, {x, 0, z}], x], 1] (* A079978 *)
u = Drop[CoefficientList[Series[1/p, {x, 0, z}], x], 1] (* A291038 *)
u/4 (* A291039 *)


CROSSREFS

Cf. A079978, A290616, A291038.
Sequence in context: A186812 A027930 A038200 * A030015 A318567 A103446
Adjacent sequences: A291036 A291037 A291038 * A291040 A291041 A291042


KEYWORD

nonn,easy


AUTHOR

Clark Kimberling, Sep 14 2017


STATUS

approved



