Diagonal sums of correlation triangle for (1+x)^3/(1-x).

Terms

a(0) =1a(1) =4a(2) =11a(3) =25a(4) =47a(5) =79a(6) =122a(7) =175a(8) =239a(9) =314a(10) =399a(11) =495a(12) =602a(13) =719a(14) =847a(15) =986a(16) =1135a(17) =1295a(18) =1466a(19) =1647a(20) =1839a(21) =2042a(22) =2255a(23) =2479a(24) =2714a(25) =2959a(26) =3215a(27) =3482a(28) =3759a(29) =4047