Sums of antidiagonals of A321960.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =54a(6) =227a(7) =1085a(8) =5774a(9) =33679a(10) =212807a(11) =1443622a(12) =10439565a(13) =80016693a(14) =646976322a(15) =5496339141a(16) =48894262619a(17) =454113866430