a(1)=a(2)=0; thereafter a(n) = a(n-2)+A238828(n-1)+A238827(n).

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =2a(5) =6a(6) =15a(7) =36a(8) =91a(9) =218a(10) =544a(11) =1325a(12) =3281a(13) =8055a(14) =19880a(15) =48930a(16) =120610a(17) =297055a(18) =731922a(19) =1802994a(20) =4441915a(21) =10942602a(22) =26957739a(23) =66410994a(24) =163606230a(25) =403049273a(26) =992926975a(27) =2446110587a(28) =6026082552a(29) =14845470456