a(n) is the smallest number k such that sigma(k) - 2k = 2^n.

Terms

a(0) =20a(1) =12a(2) =56a(3) =550a(4) =572a(5) =108a(6) =860a(7) =952a(8) =1232a(9) =6328a(10) =3708a(11) =40540a(12) =37072a(13) =79288a(14) =327260a(15) =357112a(16) =302000a(17) =527296a(18) =1764056a(19) =6506512a(20) =38559776a(21) =21893248a(22) =42257216a(23) =167771740a(24) =90798560a(25) =469761208a(26) =508198064a(27) =490304800a(28) =1353048560a(29) =2951488480