a(n) = Sum_{k=1..floor(n/2)} T(n, 2k), array T as in A049777.

Terms

a(0) =2a(1) =5a(2) =13a(3) =23a(4) =41a(5) =62a(6) =94a(7) =130a(8) =180a(9) =235a(10) =307a(11) =385a(12) =483a(13) =588a(14) =716a(15) =852a(16) =1014a(17) =1185a(18) =1385a(19) =1595a(20) =1837a(21) =2090a(22) =2378a(23) =2678a(24) =3016a(25) =3367a(26) =3759a(27) =4165a(28) =4615a(29) =5080