OFFSET
0,2
COMMENTS
For a guide to related sequences, see A211795.
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.: -x*(14+43*x+68*x^2+46*x^3+14*x^4+x^5) / ( (1+x)^3*(x-1)^5 )
MATHEMATICA
t = Compile[{{n, _Integer}},
Module[{s = 0}, (Do[If[(w < # || x < # || y < # || z > #) &[Max[w, x, y, z] - Min[w, x, y, z]], s++],
{w, 0, n}, {x, 0, n}, {y, 0, n}, {z, 0, n}]; s)]];
Map[t[#] &, Range[0, 40]] (* A212752 *)
(* Peter J. C. Moses, May 24 2012 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, May 27 2012
STATUS
approved