OFFSET
0,3
COMMENTS
Quadrisection of sequence with g.f. 1/(1-x^2-x^3), or A000931(n+3).
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2,3,1).
FORMULA
G.f.: (1-x-x^2)/(1-2x-3x^2-x^3);
a(n)=sum{k=0..2n, binomial(k, 4n-2k)};
a(n)=2a(n-1)+3a(n-2)+a(n-3);
a(n)=A000931(4n+3).
a(n) = Sum [k=0..n, C(2n-k, 2k) ].
EXAMPLE
1 + x + 4*x^2 + 12*x^3 + 37*x^4 + 114*x^5 + 351*x^6 + ...
MATHEMATICA
LinearRecurrence[{2, 3, 1}, {1, 1, 4}, 40] (* Harvey P. Dale, Aug 23 2011 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 29 2004
STATUS
approved