Duplicate of A129775.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =21a(5) =78a(6) =298a(7) =1157a(8) =4539a(9) =17936a(10) =71251a(11) =284188a(12) =1137076a(13) =4561093a(14) =18333337a(15) =73816489a(16) =297635750a(17) =1201551286a(18) =4855672249a(19) =19640147061a(20) =79501958895a(21) =322037615290