T(n,n-1), array T as in A047140.

Terms

a(0) =1a(1) =3a(2) =8a(3) =23a(4) =80a(5) =290a(6) =1010a(7) =3521a(8) =12934a(9) =48498a(10) =180020a(11) =666648a(12) =2512214a(13) =9569120a(14) =36408682a(15) =138417669a(16) =529685612a(17) =2038304708a(18) =7852427512a(19) =30259337658a(20) =116937868076a(21) =453269554872