Sets with a congruence property.

Terms

a(0) =0a(1) =4a(2) =40a(3) =468a(4) =5828a(5) =76260a(6) =1032444a(7) =14316584a(8) =202116108a(9) =2893451652a(10) =41886157564a(11) =611902123284