Diagonal sums of number triangle A109970.

Terms

a(0) =1a(1) =0a(2) =1a(3) =2a(4) =8a(5) =34a(6) =162a(7) =822a(8) =4365a(9) =23956a(10) =134814a(11) =773746a(12) =4511693a(13) =26652346a(14) =159170385a(15) =959412290a(16) =5829083420a(17) =35661048886a(18) =219491344362