Diagonal sums of number triangle A154221.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =5a(5) =9a(6) =16a(7) =32a(8) =61a(9) =125a(10) =246a(11) =502a(12) =999a(13) =2023a(14) =4040a(15) =8136a(16) =16265a(17) =32649a(18) =65290a(19) =130826a(20) =261643a(21) =523787a(22) =1047564a(23) =2096140a(24) =4192269a(25) =8386573a(26) =16773134a(27) =33550350a(28) =67100687a(29) =134209551