Partial sums of the little Schroeder numbers (A001003).

Terms

a(0) =1a(1) =2a(2) =5a(3) =16a(4) =61a(5) =258a(6) =1161a(7) =5440a(8) =26233a(9) =129282a(10) =648141a(11) =3294864a(12) =16943733a(13) =87983106a(14) =460676625a(15) =2429478144a(16) =12893056497a(17) =68802069506a(18) =368961496469