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.: ( -1-12*x-40*x^2-36*x^3-25*x^4+12*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]] (* A212751 *)
(* Peter J. C. Moses, May 24 2012 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, May 27 2012
STATUS
approved