Sum of the widths of the free polyominoes with n cells.

Terms

a(0) =1a(1) =1a(2) =3a(3) =9a(4) =29a(5) =91a(6) =322a(7) =1206a(8) =4600a(9) =17931a(10) =70577a(11) =279652a(12) =1110758a(13) =4424120a(14) =17647314a(15) =70484576a(16) =281750598a(17) =1127181327