a(n) = n * Sum_{d|n} (binomial(n,d) / gcd(n,d)).

Terms

a(0) =1a(1) =6a(2) =12a(3) =44a(4) =30a(5) =252a(6) =56a(7) =856a(8) =846a(9) =3080a(10) =132a(11) =20616a(12) =182a(13) =49532a(14) =52110a(15) =237232a(16) =306a(17) =1227096a(18) =380a(19) =4106320a(20) =2470272a(21) =15525092a(22) =552a(23) =86092176a(24) =1328900a(25) =270424752a(26) =126624006a(27) =1157002616a(28) =870a(29) =5577100260