OFFSET
0,2
REFERENCES
C. Kenneth Fan, Structure of a Hecke algebra quotient. J. Amer. Math. Soc. 10 (1997), no. 1, 139-167.
C. K. Fan, A Hecke algebra quotient and some combinatorial applications. J. Algebraic Combin. 5 (1996), no. 3, 175-189.
LINKS
Boothby, T.; Burkert, J.; Eichwald, M.; Ernst, D. C.; Green, R. M.; Macauley, M. On the cyclically fully commutative elements of Coxeter groups, J. Algebr. Comb. 36, No. 1, 123-148 (2012), Table 1 type H.
FORMULA
a(n) = A000984(n) -2^(n+2) +n+3.
-finite: -(n+1)*(131*n-245) *a(n) +2*(563*n^2-867*n-245) *a(n-1) +3*(-1099*n^2+2480*n-1105) *a(n-2) +2*(1987*n^2-5829*n+4205) *a(n-3) -4*(209*n-178)*(2*n-5) *a(n-4)=0. - R. J. Mathar, Jun 11 2019
MAPLE
seq( binomial(2*n+2, n+1)-2^(n+2)+n+3, n=0..20);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved