Interpolation of A001764(n+1) and A006629(n).

Terms

a(0) =1a(1) =1a(2) =3a(3) =4a(4) =12a(5) =18a(6) =55a(7) =88a(8) =273a(9) =455a(10) =1428a(11) =2448a(12) =7752a(13) =13566a(14) =43263a(15) =76912a(16) =246675a(17) =444015a(18) =1430715a(19) =2601300a(20) =8414640a(21) =15426840a(22) =50067108a(23) =92431584a(24) =300830572a(25) =558685348a(26) =1822766520a(27) =3402497504a(28) =11124755664a(29) =20858916870