a(n) = 2^(n+2) + 3^n + 10.

Terms

a(0) =15a(1) =21a(2) =35a(3) =69a(4) =155a(5) =381a(6) =995a(7) =2709a(8) =7595a(9) =21741a(10) =63155a(11) =185349a(12) =547835a(13) =1627101a(14) =4848515a(15) =14479989a(16) =43308875a(17) =129664461a(18) =388469075a(19) =1164358629a(20) =3490978715a(21) =10468741821a(22) =31397836835a(23) =94176733269a(24) =282496645355a(25) =847422827181