a(n) = A000292(A000292(n)).

Terms

a(0) =0a(1) =1a(2) =20a(3) =220a(4) =1540a(5) =7770a(6) =30856a(7) =102340a(8) =295240a(9) =762355a(10) =1798940a(11) =3939936a(12) =8104460a(13) =15803060a(14) =29426320a(15) =52636760a(16) =90889616a(17) =152112005a(18) =247574180a(19) =392991060a(20) =609896980a(21) =927341646a(22) =1383960600a(23) =2030479100a(24) =2932714200a(25) =4175145975a(26) =5865135276a(27) =8137872120