a(n) = (n^3+5*n+3)/3 + 2*floor(n/2) + a(n-2), with a(0)=1 and a(1)=3.

Terms

a(0) =1a(1) =3a(2) =10a(3) =20a(4) =43a(5) =75a(6) =132a(7) =208a(8) =325a(9) =475a(10) =686a(11) =948a(12) =1295a(13) =1715a(14) =2248a(15) =2880a(16) =3657a(17) =4563a(18) =5650a(19) =6900a(20) =8371a(21) =10043a(22) =11980a(23) =14160a(24) =16653a(25) =19435a(26) =22582a(27) =26068a(28) =29975a(29) =34275