Second diagonal of A027538.

Terms

a(0) =7a(1) =52a(2) =231a(3) =806a(4) =2451a(5) =6840a(6) =18031a(7) =45682a(8) =112443a(9) =270788a(10) =641031a(11) =1496574a(12) =3453859a(13) =7893232a(14) =17886687a(15) =40233578a(16) =89908875a(17) =199746108a(18) =441441655a(19) =970971190a(20) =2126500467a(21) =4638886952a(22) =10083091791a(23) =21843918306a(24) =47177512411a(25) =101602798900a(26) =218238002151a(27) =467614538222