First differences of A047780.

Terms

a(0) =1a(1) =9a(2) =47a(3) =183a(4) =560a(5) =1426a(6) =3164a(7) =6322a(8) =11643a(9) =20095a(10) =32901a(11) =51569a(12) =77922a(13) =114128a(14) =162730a(15) =226676a(16) =309349a(17) =414597a(18) =546763a(19) =710715a(20) =911876a(21) =1156254a(22) =1450472a(23) =1801798a(24) =2218175a(25) =2708251a(26) =3281409a(27) =3947797a(28) =4718358a(29) =5604860