a(n) = Sum_{i=0..2n} (-1)^i * T(i,2n-i), array T as in A049735.

Terms

a(0) =1a(1) =17a(2) =49a(3) =125a(4) =213a(5) =361a(6) =433a(7) =617a(8) =805a(9) =1029a(10) =1345a(11) =1585a(12) =1801a(13) =2149a(14) =2461a(15) =2977a(16) =3305a(17) =3709a(18) =4013a(19) =4557a(20) =5057a(21) =5689a(22) =6085a(23) =6661a(24) =7117a(25) =8025a(26) =8689a(27) =9205a(28) =10005a(29) =10649