OFFSET
0,2
LINKS
A. Burstein and T. Mansour, Words restricted by 3-letter generalized multipermutation patterns, Annals. Combin., 7 (2003), 1-14. See Th. 3.12.
FORMULA
The g.f. can be written as either
1/(1-x*(1+1/(1+x^2)+1/(1+2*x^2)+1/(1+3*x^2)+1/(1+4*x^2)+1/(1+5*x^2)))
or
-(1+x^2)*(1+2*x^2)*(1+3*x^2)*(1+4*x^2)*(1+5*x^2)/(-1-15*x^2-85*x^4-225*x^6-274*x^8-120*x^10+6*x+120*x^11+548*x^9+675*x^7+340*x^5+75*x^3)
MAPLE
F312:=proc(k) local j, t1;
t1:=add(1/(1+j*x^2), j=0..k-1);
1/(1-x*t1);
end;
seriestolist(series(F312(6), x, 40));
MATHEMATICA
CoefficientList[1/(1 - x*Sum[1/(1 + j*x^2), {j, 0, 5}]) + O[x]^30, x] (* Jean-François Alcover, Nov 24 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 21 2013
STATUS
approved