Number of intersection points of all lines through pairs of vertices of a regular n-gon.

Terms

a(0) =3a(1) =5a(2) =15a(3) =37a(4) =91a(5) =145a(6) =333a(7) =471a(8) =891a(9) =901a(10) =1963a(11) =2185a(12) =3795a(13) =3969a(14) =6681a(15) =5563a(16) =10963a(17) =11141a(18) =17031a(19) =17293a(20) =25323a(21) =21913a(22) =36325a(23) =36479a(24) =50571a(25) =50485a(26) =68643a(27) =51661a(28) =91171a(29) =90753