A transform of the central binomial coefficients A001405.

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =17a(5) =43a(6) =109a(7) =279a(8) =721a(9) =1871a(10) =4881a(11) =12783a(12) =33585a(13) =88495a(14) =233745a(15) =618719a(16) =1640833a(17) =4358719a(18) =11595841a(19) =30890751a(20) =82391297a(21) =219995007a(22) =588004737a(23) =1573072383a(24) =4211960065a(25) =11286490879a(26) =30265474305a(27) =81213330175a(28) =218061109505a(29) =585844009727