a(n) = 2*(n-1)*a(n-1) - a(n-2) + 2*(n-2)*a(n-3) with a(0)=a(1)=a(2)=1.
A269820
a(n) = 2*(n-1)*a(n-1) - a(n-2) + 2*(n-2)*a(n-3) with a(0)=a(1)=a(2)=1.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =5a(4) =33a(5) =265a(6) =2657a(7) =31949a(8) =447809a(9) =7170193a(10) =129126849a(11) =2583427349a(12) =56849678689
External references
- oeis: A269820