261293

Appears in sequences

• The number of 321- and 2143-avoiding permutations of length n.at n=16A088921
• Expansion of g.f.: x^3*(1 + 4*x - x^2 - 6*x^3 + x^4)/(1 - 9*x^2 - 3*x^3 + 17*x^4 + 8*x^5 - 6*x^6 - 7*x^7 + x^8 - x^9).at n=15A173652