a(n) = Min {x : sigma(x) = phi(n*x), x is not a prime}, least nonprime solutions to sigma(x) = phi(n*x).

A087979

a(n) = Min {x : sigma(x) = phi(n*x), x is not a prime}, least nonprime solutions to sigma(x) = phi(n*x).

Terms

    a(0) =1a(1) =1a(2) =15a(3) =14a(4) =14a(5) =6a(6) =6a(7) =42a(8) =30a(9) =42a(10) =168a(11) =210a(12) =210a(13) =420a(14) =840a(15) =20790a(16) =20790a(17) =9240a(18) =9240a(19) =83160a(20) =120120a(21) =3984120a(22) =5165160a(23) =43825320a(24) =26860680a(25) =43825320a(26) =1304863560a(27) =569729160a(28) =569729160a(29) =16522145640

External references