OFFSET
0,2
COMMENTS
LINKS
Index entries for linear recurrences with constant coefficients, signature (2,2,-6,0,6,-2,-2,1)
FORMULA
a(n) = 2*a(n-1)+2*a(n-2)-6*a(n-3)+6*a(n-5)-2*a(n-6)-2*a(n-7)+a(n-8).
G.f.: ( -1-13*x-47*x^2-57*x^3-47*x^4-3*x^5-x^6+x^7 ) / ( (1+x)^3*(x-1)^5 ).
MATHEMATICA
t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[Max[w, x, y, z] >= 2 Min[w, x, y, z], s = s + 1],
{w, 0, n}, {x, 0, n}, {y, 0, n}, {z, 0, n}]; s)]];
Map[t[#] &, Range[0, 40]] (* A212741 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, May 26 2012
STATUS
approved