OFFSET
1,4
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..20000
EXAMPLE
The seven proper divisors of 24 are 1, 2, 3, 4, 6, 8, 12. All except 12 are nonabundant (in A263837), thus a(24) = 6.
MATHEMATICA
a[n_] := DivisorSum[n, 1 &, # < n && DivisorSigma[1, #] <= 2*# &]; Array[a, 100] (* Amiram Eldar, Mar 14 2024 *)
PROG
(PARI) A294928(n) = sumdiv(n, d, (d<n)*(sigma(d)<=(2*d)));
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 14 2017
STATUS
approved