a(n) = Sum_{k=0..floor(n/2)} A026626(n, k).

Terms

a(0) =1a(1) =1a(2) =4a(3) =5a(4) =15a(5) =22a(6) =59a(7) =90a(8) =230a(9) =362a(10) =902a(11) =1450a(12) =3551a(13) =5802a(14) =14022a(15) =23210a(16) =55492a(17) =92842a(18) =219974a(19) =371370a(20) =873101a(21) =1485482a(22) =3468893a(23) =5941930a(24) =13793183a(25) =23767722a(26) =54880915a(27) =95070890a(28) =218480607a(29) =380283562