a(n) is the least composite x such that sigma(x) divides (x-1)^n but not (x-1)^(n-1), for n >= 2.

Terms

a(0) =385a(1) =21a(2) =93a(3) =235a(4) =2899a(5) =903a(6) =1771a(7) =3619a(8) =651a(9) =11935a(10) =2667a(11) =48895a(12) =11811a(13) =27559a(14) =415555a(15) =848995a(16) =172011a(17) =3153535a(18) =761763a(19) =1777447a(20) =2752491a(21) =7281799a(22) =11010027a(23) =28442407a(24) =48758691a(25) =113770279a(26) =199753347a(27) =466091143a(28) =677207307a(29) =2064117919