a(n) = 8n+5^n-3^n.

Terms

a(0) =0a(1) =10a(2) =32a(3) =122a(4) =576a(5) =2922a(6) =14944a(7) =75994a(8) =384128a(9) =1933514a(10) =9706656a(11) =48651066a(12) =243609280a(13) =1219108906a(14) =6098732768a(15) =30503229338a(16) =152544844032a(17) =762810313098