a(n) is the denominator of the sum of the reciprocals of the first n squarefree numbers.

Terms

a(0) =1a(1) =2a(2) =6a(3) =30a(4) =5a(5) =35a(6) =70a(7) =770a(8) =10010a(9) =5005a(10) =15015a(11) =255255a(12) =4849845a(13) =1616615a(14) =3233230a(15) =74364290a(16) =37182145a(17) =1078282205a(18) =6469693230a(19) =200560490130a(20) =6077590610a(21) =3038795305a(22) =607759061a(23) =22487085257a(24) =44974170514a(25) =134922511542a(27) =921970495537