OFFSET
1,1
COMMENTS
A number k is (2n-1)-abundant if sum_{d|k, d<k} (2*d-1) > 2*k-1, a specialization of the definition in A175522.
Adding 2k-1 on both sides of the condition yields the equivalent condition A129246(k) > 2*(2k-1).
Adding 2k-1 on both sides also yields sum_{d|k} (2*d-1) > 2*(2k-1), equivalent to 2*sum_{d|k}d - tau(k) > 2*(2k-1) or sigma(k) > 2k-1+tau(k)/2, equivalent to A033880(k) > tau(k)/2-1.
MATHEMATICA
aQ[n_] := DivisorSum[n, 2#-1&, #<n&] > 2n-1; Select[Range[252], aQ] (* Amiram Eldar, Feb 18 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Dec 05 2010
EXTENSIONS
More terms from Amiram Eldar, Feb 18 2019
STATUS
approved