a(n) = lcm(1,2,3,...,n) * (sum of Farey fractions of order n).

Terms

a(0) =1a(1) =3a(2) =15a(3) =42a(4) =330a(5) =390a(6) =3990a(7) =9660a(8) =36540a(9) =41580a(10) =595980a(11) =651420a(12) =10630620a(13) =11711700a(14) =13153140a(15) =29189160a(16) =594233640a(17) =630990360a(18) =14083949880a(19) =15015120120a(20) =16411875480a(21) =17575838280a(22) =463140798120a(23) =484557713640