Denominator(sum(i=1,n,1/i^4))/denominator(sum(i=1,n,1/i^3)).

Terms

a(0) =1a(1) =2a(2) =6a(3) =12a(4) =60a(5) =540a(6) =3780a(7) =7560a(8) =2520a(9) =2520a(10) =27720a(11) =27720a(12) =360360a(13) =360360a(14) =360360a(15) =720720a(16) =12252240a(17) =110270160a(18) =2095133040a(19) =10475665200a(20) =1496523600a(21) =1496523600a(22) =34420042800a(23) =34420042800a(24) =34420042800a(25) =34420042800