a(n) = Sum_{i=0..n} T(i,n-i), array T as in A049723.

Terms

a(0) =1a(1) =8a(2) =24a(3) =62a(4) =117a(5) =210a(6) =339a(7) =498a(8) =708a(9) =1002a(10) =1328a(11) =1730a(12) =2185a(13) =2752a(14) =3404a(15) =4140a(16) =4958a(17) =5902a(18) =6947a(19) =8136a(20) =9423a(21) =10826a(22) =12406a(23) =14114a(24) =15919a(25) =17948a(26) =20141a(27) =22494a(28) =24970a(29) =27670