A256056(n)/2.

Terms

a(0) =-1a(1) =2a(2) =3a(3) =5a(4) =10a(5) =15a(6) =21a(7) =34a(8) =48a(9) =65a(10) =94a(11) =129a(12) =175a(13) =237a(14) =312a(15) =413a(16) =545a(17) =705a(18) =907a(19) =1169a(20) =1491a(21) =1887a(22) =2387a(23) =2997a(24) =3747a(25) =4674a(26) =5793a(27) =7160a(28) =8827a(29) =10827