First column (also row sums) of triangle in A099964.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =8a(6) =17a(7) =39a(8) =126a(9) =352a(10) =1026a(11) =2943a(12) =11429a(13) =39138a(14) =138903a(15) =486490a(16) =1711141a(17) =7720713a(18) =31383260a(19) =131236182a(20) =543056039a(21) =2254646235a(22) =9349845765a(23) =48137959377a(24) =226341090088