Diagonal sums of number triangle A109974.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =7a(5) =16a(6) =19a(7) =46a(8) =66a(9) =159a(10) =274a(11) =667a(12) =1320a(13) =3263a(14) =7156a(15) =18084a(16) =42794a(17) =111018a(18) =278752a(19) =743889a(20) =1959482a(21) =5383395a(22) =14761634a(23) =41740307a(24) =118517301a(25) =344580865a(26) =1009349749a(27) =3013665637a(28) =9081346743a(29) =27808754039