Second column and subdiagonal of number triangle A098509.

Terms

a(0) =1a(1) =1a(2) =1a(3) =5a(4) =7a(5) =42a(6) =22a(7) =429a(8) =715a(9) =4862a(10) =8398a(11) =58786a(12) =52003a(13) =742900a(14) =1337220a(15) =646323a(16) =17678835a(17) =129644790a(18) =79606450a(19) =1767263190a(20) =328206021a(21) =8155422340a(22) =45741281820a(23) =343059613650a(24) =107492012277