OFFSET
5,1
LINKS
S. Kitaev, J. Remmel and M. Tiefenbruck, Marked mesh patterns in 132-avoiding permutations I, arXiv preprint arXiv:1201.6243, 2012
Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1).
FORMULA
For n>=5, a(n)=(n^2-2n-8)(n^2-2n-3)/6 or a(n)=(n-4)*A212346(n-1).
G.f.: -2*x^5*(2*x^2-7*x+7) / (x-1)^5. - Colin Barker, Jul 22 2013
MATHEMATICA
QQ0[t, x] = (1 - (1-4*x*t)^(1/2)) ) / (2*x*t); QQ1[t, x] = 1/(1 - t*QQ0[t, x]); QQ2[t, x] = (1 + t*(QQ1[t, x] - QQ0[t, x]))/(1 - t*QQ0[t, x]); QQ3[t, x] = (1 + t*(QQ2[t, x] - QQ0[t, x] + t*(QQ1[t, x] - QQ0[t, x])))/(1 - t*QQ0[t, x]); QQ4[t, x] = (1 + t*(QQ3[t, x] - QQ0[t, x] + t*(QQ2[t, x] - QQ0[t, x]) + (2*t^2*(QQ1[t, x] - QQ0[t, x]))))/(1 - t*QQ0[t, x]); CoefficientList[Coefficient[Simplify[Series[QQ4[t, x], {t, 0, 35}]], x], t] (* Robert Price, Jun 04 2012 *)
Table[(n-4)*(n-3)*(n+1)*(n+2)/6, {n, 5, 50}] (* Jean-François Alcover, Sep 21 2017 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, May 09 2012
EXTENSIONS
a(10)-a(35) from Robert Price, Jun 02 2012
STATUS
approved