a(n) = 6^n - 5^n + 4^n.

Terms

a(0) =1a(1) =5a(2) =27a(3) =155a(4) =927a(5) =5675a(6) =35127a(7) =218195a(8) =1354527a(9) =8386715a(10) =51749127a(11) =318163235a(12) =1949418927a(13) =11907099755a(14) =72529083927a(15) =440741148275