a(n) = 5*a(n-1) - 4*a(n-3) for n >= 4, where a(1) = 1, a(2) = 4, a(3) = 18.

A341248

a(n) = 5*a(n-1) - 4*a(n-3) for n >= 4, where a(1) = 1, a(2) = 4, a(3) = 18.

Terms

    a(0) =1a(1) =4a(2) =18a(3) =86a(4) =414a(5) =1998a(6) =9646a(7) =46574a(8) =224878a(9) =1085806a(10) =5242734a(11) =25314158a(12) =122227566a(13) =590166894a(14) =2849577838a(15) =13758978926a(16) =66434227054a(17) =320772823918

External references