OFFSET

1,3

COMMENTS

usigma(m) is the sum of unitary divisors of m, A034448.

LINKS

Daniel Suteu, Table of n, a(n) for n = 1..10000

EXAMPLE

a(12) = 11 because the unitary divisors of 11 are 1 and 11, and their sum is 12.

MATHEMATICA

usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); a[n_] := Module[{k = n}, While[k > 0 && usigma[k] != n, k--]; k]; Array[a, 100] (* Amiram Eldar, Aug 27 2024 *)

CROSSREFS

KEYWORD

nonn

AUTHOR

Labos Elemer, Sep 05 2001

EXTENSIONS

Corrected by Don Reble, May 14 2006

STATUS

approved