Third differences of A000219.

Terms

a(0) =-1a(1) =3a(2) =0a(3) =9a(4) =1a(5) =22a(6) =12a(7) =48a(8) =45a(9) =120a(10) =125a(11) =290a(12) =354a(13) =676a(14) =913a(15) =1611a(16) =2232a(17) =3757a(18) =5349a(19) =8597a(20) =12462a(21) =19476a(22) =28325a(23) =43445a(24) =63328a(25) =95462a(26) =139139a(27) =207171a(28) =301022a(29) =443779