A064596 Smallest nonunitary multiperfect number of index n; i.e., smallest k such that sigma(k) - usigma(k) = nk.

1, 24, 2520, 186076800

Offset: 0

Author

Dean Hickerson, Sep 25 2001

Keywords

• nonn
• hard
• more

Comments

4.5*10^14 < a(4) <= 1081895452249824576000.

Crossrefs

Cf. A048146, A064591, A064592, A064593, A064594, A064595.

Programs

Mathematica

nusigma[ n_ ] := DivisorSigma[ 1, n ]-Times@@(1+Power@@#&/@FactorInteger[ n ]); a[ n_ ] := For[ k=1, True, k++, If[ nusigma[ k ]==n k, Return[ k ] ] ]