OFFSET
1,2
LINKS
Liu Yanpei, On the number of rooted c-nets, J. Combin. Theory, B 36 (1984), 118-123. See the sequence R_n.
FORMULA
A000287(n) = (-1)^n*2 + a(n-1).
MAPLE
R:=proc(n) option remember; if n=1 then -1 elif n=2 then 2 else
(1/(2*n))*((7*n-22)*R(n-1)+2*(2*n-1)*R(n-2)); fi; end;
[seq(R(n), n=1..40)];
MATHEMATICA
a[n_] := a[n] = Which[n == 1, -1, n == 2, 2, True, (1/(2*n))*((7*n-22)*a[n-1]+2*(2*n-1)*a[n-2])]; Table[a[n], {n, 1, 40}] (* Jean-François Alcover, Mar 06 2014, after Maple *)
CROSSREFS
KEYWORD
sign
AUTHOR
N. J. A. Sloane, Mar 28 2012
STATUS
approved