a(n) = 4*A061547(n+1) - 3*A166753(n).

Terms

a(0) =1a(1) =2a(2) =9a(3) =22a(4) =53a(5) =114a(6) =241a(7) =494a(8) =1005a(9) =2026a(10) =4073a(11) =8166a(12) =16357a(13) =32738a(14) =65505a(15) =131038a(16) =262109a(17) =524250a(18) =1048537a(19) =2097110a(20) =4194261a(21) =8388562a(22) =16777169a(23) =33554382a(24) =67108813a(25) =134217674a(26) =268435401a(27) =536870854a(28) =1073741765a(29) =2147483586