a(n) = 5^n - 2^n + 1^n.

Terms

a(0) =1a(1) =4a(2) =22a(3) =118a(4) =610a(5) =3094a(6) =15562a(7) =77998a(8) =390370a(9) =1952614a(10) =9764602a(11) =48826078a(12) =244136530a(13) =1220694934a(14) =6103499242a(15) =30517545358a(16) =152587825090a(17) =762939322054