A111586 G.f.: -x*(1+x+x^2+2*x^3+3*x^4+3*x^5+x^6-x^7-x^9)/((1+x)*(-1+2*x+x^3)).

0, 1, 2, 5, 12, 28, 62, 136, 299, 661, 1456, 3213, 7085, 15628, 34467, 76021, 167668, 369805, 815629, 1798928, 3967659, 8750949, 19300824, 42569309, 93889565, 207079956, 456729219, 1007348005, 2221775964, 4900281149, 10807910301, 23837596568, 52575474283, 115958858869

Offset: 0

Author

N. J. A. Sloane, Nov 17 2005

Keywords

• nonn

References

• V. Vatter, The Enumeration and Structure of Permutation Classes, Ph. D. Dissertation, Rutgers Univ., Math. Dept., 2006.

Links

• Index entries for linear recurrences with constant coefficients, signature (1,2,1,1).

Formula

a(n) = 2*a(n-1) + a(n-3) - 2*(-1)^n for n >= 10. - Greg Dresden, May 18 2020