Triangle of series-parallel numbers.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =2a(6) =4a(7) =6a(8) =8a(9) =8a(10) =10a(11) =18a(12) =34a(13) =52a(14) =52a(15) =24a(16) =58a(17) =136a(18) =288a(19) =472a(20) =472a(21) =66a(22) =186a(23) =538a(24) =1424a(25) =3224a(26) =5504a(27) =5504a(28) =180a(29) =614