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

Terms

a(0) =1a(1) =11a(2) =23a(3) =79a(4) =223a(5) =703a(6) =2175a(7) =6911a(8) =22015a(9) =70655a(10) =227327a(11) =733183a(12) =2367487a(13) =7651327a(14) =24739839a(15) =80019455a(16) =258867199a(17) =837550079a(18) =2710044671a(19) =8769241087a(20) =28376563711a(21) =91825897471a(22) =297149661183a(23) =961586135039