OFFSET
0,7
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,1,0,0,-2,0,0,1,1,-1).
FORMULA
a(n) = a(n-1) + a(n-2) - 2*a(n-5) + a(n-8) + a(n-9) - a(n-10).
G.f.: 12*(x^6 + 3*x^7 + 3*x^8 + 5*x^9)/(1 - x - x^2 + 2*x^5 - x^8 - x^9 + x^10).
MATHEMATICA
t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[Length[Union[{w, x, y, Abs[w - x], Abs[x - y], Abs[y - w]}]] ==
6, s = s + 1], {w, 0, n}, {x, 0, n}, {y, 0, n}]; s)]];
m = Map[t[#] &, Range[0, 60]] (* this sequence *)
m/12 (* A213494 *)
LinearRecurrence[{1, 1, 0, 0, -2, 0, 0, 1, 1, -1}, {0, 0, 0, 0, 0, 0, 12, 48, 96, 204}, 60]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jun 13 2012
STATUS
approved