a(n) = A297628(n,1).

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =20a(5) =137a(6) =1478a(7) =22925a(8) =481448a(9) =13138193a(10) =451749962a(11) =19104365333a(12) =974417603132