a(n) = A002861(n) + A000081(n).

Terms

a(0) =2a(1) =3a(2) =6a(3) =13a(4) =29a(5) =71a(6) =173a(7) =444a(8) =1148a(9) =3030a(10) =8059a(11) =21715a(12) =58836a(13) =160687a(14) =441083a(15) =1217134a(16) =3372386a(17) =9380948a(18) =26180962a(19) =73292358a(20) =205731862a(21) =578922864a(22) =1632707684a(23) =4614098810a(24) =13064064882a(25) =37052720050a(26) =105257568244a(27) =299452309023a(28) =853094139960