INVERTi transform of A006973.

Terms

a(0) =1a(1) =1a(2) =6a(3) =7a(4) =78a(5) =420a(6) =6872a(7) =17253a(8) =326552a(9) =2680988a(10) =33949242a(11) =386091406a(12) =5974089338a(13) =67562271804