Denominator of Sum_{1<=j<=k<=n, gcd(j,k)=1} 1/(j*k).

Terms

a(0) =1a(1) =2a(2) =1a(3) =3a(4) =4a(5) =20a(6) =10a(7) =210a(8) =168a(9) =504a(10) =105a(11) =1155a(12) =792a(13) =1560a(14) =60060a(15) =180180a(16) =16016a(17) =123760a(18) =510510a(19) =29099070a(20) =21162960a(21) =335920a(22) =3233230a(23) =74364290a(24) =45762640a(25) =187210800a(26) =13385572200a(27) =40156716600a(28) =97349616a(29) =31054527504