a(n) = 2^n - Fibonacci(n).

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =13a(5) =27a(6) =56a(7) =115a(8) =235a(9) =478a(10) =969a(11) =1959a(12) =3952a(13) =7959a(14) =16007a(15) =32158a(16) =64549a(17) =129475a(18) =259560a(19) =520107a(20) =1041811a(21) =2086206a(22) =4176593a(23) =8359951a(24) =16730848a(25) =33479407a(26) =66987471a(27) =134021310a(28) =268117645a(29) =536356683