a(n) = Sum_{i=0..2n} (-1)^i * T(i,2n-i), array T as in A049723.

Terms

a(0) =1a(1) =12a(2) =29a(3) =69a(4) =116a(5) =192a(6) =229a(7) =324a(8) =418a(9) =533a(10) =695a(11) =818a(12) =923a(13) =1099a(14) =1258a(15) =1520a(16) =1687a(17) =1893a(18) =2044a(19) =2315a(20) =2567a(21) =2890a(22) =3090a(23) =3377a(24) =3604a(25) =4062a(26) =4397a(27) =4659a(28) =5066a(29) =5384