Diagonal sums of symmetric triangle A108350.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =5a(5) =8a(6) =14a(7) =24a(8) =43a(9) =77a(10) =140a(11) =255a(12) =467a(13) =856a(14) =1572a(15) =2888a(16) =5309a(17) =9761a(18) =17950a(19) =33011a(20) =60713a(21) =111664a(22) =205378a(23) =377744a(24) =694775a(25) =1277885a(26) =2350392a(27) =4323039a(28) =7951303a(29) =14624720