Least number k such that sigma(k) >= 2^n.

Terms

a(0) =2a(1) =3a(2) =6a(3) =10a(4) =18a(5) =30a(6) =60a(7) =108a(8) =180a(9) =360a(10) =720a(11) =1260a(12) =2520a(13) =5040a(14) =9240a(15) =17640a(16) =35280a(17) =65520a(18) =131040a(19) =257040a(20) =498960a(21) =982800a(22) =1884960a(23) =3603600a(24) =7207200a(25) =14414400a(26) =28274400a(27) =56548800a(28) =110270160a(29) =220540320