a(n) = n*a(n-1)+4*a(n-2)-4*(n-2)*a(n-3).

Terms

a(0) =0a(1) =1a(2) =2a(3) =10a(4) =40a(5) =216a(6) =1296a(7) =9136a(8) =73088a(9) =658048a(10) =6580480a(11) =72386304a(12) =868635648a(13) =11292267520a(14) =158091745280