OFFSET
0,8
LINKS
Index entries for linear recurrences with constant coefficients, signature (2,1,0,-6,-4,16,-8).
FORMULA
a(n) = 2*a(n-1) + a(n-2) - 6*a(n-4) - 4*a(n-5) + 16*a(n-6) - 8*a(n-7).
G.f.: x^6/((-1 + x)^2 (-1 + 2 x^2) (-1 + 4 x^3)).
MATHEMATICA
s[n_] := s[n] = Select[Subsets[Range[n]], Length[#] >= 3 &];
a[n_] := Select[s[n], #[[1]] + #[[2]] + #[[3]] == #[[-1]] &]
(1/4)*Table[Length[a[n]], {n, 0, 15}]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Oct 02 2022
STATUS
approved