First differences of A137976 after having added two leading ones.

Terms

a(0) =0a(1) =2a(2) =10a(3) =21a(4) =110a(5) =233a(6) =1220a(7) =2584a(8) =13530a(9) =28657a(10) =150050a(11) =317811a(12) =1664080a(13) =3524578a(14) =18454930a(15) =39088169a(16) =204668310a(17) =433494437a(18) =2269806340a(19) =4807526976a(20) =25172538050a(21) =53316291173a(22) =279167724890a(23) =591286729879