a(n) = 2 * (4^n + 2^n) + 1.

Terms

a(0) =5a(1) =13a(2) =41a(3) =145a(4) =545a(5) =2113a(6) =8321a(7) =33025a(8) =131585a(9) =525313a(10) =2099201a(11) =8392705a(12) =33562625a(13) =134234113a(14) =536903681a(15) =2147549185a(16) =8590065665a(17) =34360000513a(18) =137439477761a(19) =549756862465