Diagonal sums of a Delannoy related triangle.

Terms

a(0) =1a(1) =3a(2) =14a(3) =68a(4) =347a(5) =1819a(6) =9712a(7) =52532a(8) =286905a(9) =1578679a(10) =8738278a(11) =48601968a(12) =271406347a(13) =1520725095a(14) =8545396208a(15) =48138689272a(16) =271768537793