The sum of denominators of unreduced mediants in Farey sequences of orders 1,2,..,n.

Terms

a(0) =2a(1) =6a(2) =16a(3) =34a(4) =72a(5) =122a(6) =214a(7) =338a(8) =516a(9) =734a(10) =1062a(11) =1438a(12) =1970a(13) =2586a(14) =3322a(15) =4186a(16) =5322a(17) =6566a(18) =8152a(19) =9898a(20) =11896a(21) =14114a(22) =16838a(23) =20254a(24) =23982a(25) =28196a(26) =32746a(27) =38108a(28) =43710a(29) =50242