Diagonal sums of number triangle A186020.

Terms

a(0) =1a(1) =1a(2) =3a(3) =6a(4) =19a(5) =62a(6) =239a(7) =1013a(8) =4723a(9) =23870a(10) =129779a(11) =753784a(12) =4651285a(13) =30349577a(14) =208575027a(15) =1504582526a(16) =11358446495a(17) =89501837358a(18) =734420232291