OFFSET
0,5
COMMENTS
For a guide to related sequences, see A211422.
LINKS
Bo Gyu Jeong, Table of n, a(n) for n = 0..5000
Index entries for linear recurrences with constant coefficients, signature (0,1,1,1,-1,-1,-1,0,1).
FORMULA
a(n) = a(n-2)+a(n-3)+a(n-4)-a(n-5)-a(n-6)-a(n-7)+a(n-9).
G.f.: x^2*(1+x+2*x^2+x^3+x^4+x^5+x^6)/((1+x^2)*(1+x+x^2)*(1+x)^2*(1-x)^3). [Bruno Berselli, Jun 15 2012]
MATHEMATICA
t[n_] := t[n] = Flatten[Table[2 w - 3 x + 4 y, {w, 1, n}, {x, 1, n}, {y, 1, n}]]
c[n_] := Count[t[n], 0]
t = Table[c[n], {n, 0, 80}] (* A211541 *)
FindLinearRecurrence[t]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Apr 15 2012
STATUS
approved