2*A259322(n).

Terms

a(0) =2a(1) =1460a(2) =32710a(3) =268008a(4) =1330890a(5) =4874012a(6) =14527630a(7) =37308880a(8) =85584018a(9) =179675780a(10) =351208022a(11) =647279800a(12) =1135561050a(13) =1910402028a(14) =3100048670a(15) =4875056032a(16) =7457991970a(17) =11134523220a(18) =16265976038a(19) =23303463560a(20) =32803672042a(21) =45446398140a(22) =62053929390a(23) =83612360048a(24) =111294934450a(25) =146487510052