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

Terms

a(0) =1a(1) =3a(2) =7a(3) =16a(4) =37a(5) =86a(6) =199a(7) =456a(8) =1033a(9) =2314a(10) =5131a(11) =11276a(12) =24589a(13) =53262a(14) =114703a(15) =245776a(16) =524305a(17) =1114130a(18) =2359315a(19) =4980756a(20) =10485781a(21) =22020118a(22) =46137367a(23) =96469016a(24) =201326617a(25) =419430426a(26) =872415259a(27) =1811939356a(28) =3758096413