Partial sums of A004111.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =5a(5) =8a(6) =14a(7) =26a(8) =51a(9) =103a(10) =216a(11) =463a(12) =1011a(13) =2237a(14) =5007a(15) =11306a(16) =25732a(17) =58941a(18) =135792a(19) =314410a(20) =731258a(21) =1707554a(22) =4001778a(23) =9409162a(24) =22189556a(25) =52472676a(26) =124397323a(27) =295594279a(28) =703904947a(29) =1679567427