A Fielder sequence.

Terms

a(0) =1a(1) =3a(2) =7a(3) =15a(4) =26a(5) =57a(6) =106a(7) =207a(8) =403a(9) =788a(10) =1530a(11) =2985a(12) =5812a(13) =11322a(14) =22052a(15) =42959a(16) =83675a(17) =162993a(18) =317491a(19) =618440a(20) =1204651a(21) =2346534a(22) =4570791a(23) =8903409a(24) =17342876a(25) =33782050a(26) =65803777a(27) =128178646a(28) =249678140a(29) =486346022