a(n) = a(n-1) + 2^(A047258(n)) for n>1, a(1)=1.

Terms

a(0) =1a(1) =17a(2) =49a(3) =113a(4) =1137a(5) =3185a(6) =7281a(7) =72817a(8) =203889a(9) =466033a(10) =4660337a(11) =13048945a(12) =29826161a(13) =298261617a(14) =835132529a(15) =1908874353a(16) =19088743537a(17) =53448481905a(18) =122167958641