Numbers k such that phi(k) + sigma(k) = 4*k.

Terms

a(0) =23760a(1) =59400a(2) =153720a(3) =4563000a(4) =45326160a(5) =113315400a(6) =402831360a(7) =731601000a(8) =803685120a(9) =865950624a(10) =919501200a(11) =1178491680a(12) =3504597120a(13) =3786686400a(14) =6429564000a(15) =14924714400a(16) =25310621952a(17) =26998616736a(18) =53138687040a(19) =86955675840a(20) =513969369984