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

Terms

a(0) =1a(1) =2a(2) =4a(3) =9a(4) =22a(5) =55a(6) =136a(7) =329a(8) =778a(9) =1803a(10) =4108a(11) =9229a(12) =20494a(13) =45071a(14) =98320a(15) =213009a(16) =458770a(17) =983059a(18) =2097172a(19) =4456469a(20) =9437206a(21) =19922967a(22) =41943064a(23) =88080409a(24) =184549402a(25) =385875995a(26) =805306396a(27) =1677721629a(28) =3489660958a(29) =7247757343