Diagonal sums of A081130.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =4a(5) =13a(6) =44a(7) =162a(8) =643a(9) =2724a(10) =12259a(11) =58423a(12) =293902a(13) =1555743a(14) =8640526a(15) =50222288a(16) =304792741a(17) =1927313470a(18) =12673784445a(19) =86517541197a(20) =612134881624