Number of triple-crossings of diagonals in the regular 2n-gon.

Terms

a(0) =0a(1) =1a(2) =12a(3) =30a(4) =128a(5) =147a(6) =264a(7) =1056a(8) =600a(9) =825a(10) =2380a(11) =1482a(12) =1932a(13) =9635a(14) =3024a(15) =3672a(16) =8484a(17) =5301a(18) =6300a(19) =19474a(20) =8580a(21) =9867a(22) =20744a(23) =12900a(24) =14664a(25) =30141a(26) =18564a(27) =20706a(28) =62200a(29) =25575