Number of edges in a Farey fan of order n.

Terms

a(0) =4a(1) =9a(2) =18a(3) =30a(4) =52a(5) =74a(6) =112a(7) =154a(8) =210a(9) =268a(10) =352a(11) =436a(12) =552a(13) =668a(14) =802a(15) =948a(16) =1134a(17) =1316a(18) =1546a(19) =1778a(20) =2038a(21) =2306a(22) =2630a(23) =2952a(24) =3326a(25) =3704a(26) =4124a(27) =4556a(28) =5060a(29) =5552