Diagonal sums of number triangle A107030.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =7a(5) =12a(6) =25a(7) =56a(8) =145a(9) =422a(10) =1389a(11) =5072a(12) =20283a(13) =87996a(14) =412663a(15) =2087868a(16) =11361831a(17) =66155642a(18) =409567833a(19) =2680486870a(20) =18465061963a(21) =133504614880