OFFSET
1,1
COMMENTS
Equivalently, numbers that are equal to the sum of their nonunitary divisors, with one of them taken with a minus sign.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
48 is a term since 48 = 2 - 4 + 6 + 8 + 12 + 24 is the sum of its nonunitary divisors with one of them, 4, taken with a minus sign.
MATHEMATICA
usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); nusigma[n_] := DivisorSigma[1, n] - usigma[n]; nuAdmQ[n_] := (ab = nusigma[n] - n) > 0 && EvenQ[ab] && ab/2 < n && !CoprimeQ[ab/2, 2*n/ab]; Select[Range[1000], nuAdmQ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, May 26 2020
STATUS
approved