Triangular array related to tennis ball problem, read by rows.

Terms

a(0) =0a(1) =0a(2) =1a(3) =0a(4) =1a(5) =3a(6) =0a(7) =1a(8) =4a(9) =10a(10) =0a(11) =1a(12) =5a(13) =15a(14) =31a(15) =0a(16) =1a(17) =6a(18) =21a(19) =52a(20) =105a(21) =0a(22) =1a(23) =7a(24) =28a(25) =80a(26) =185a(27) =343a(28) =0a(29) =1