OFFSET
1,12
COMMENTS
Sum of divisors n smaller than n that are nondeficient numbers (in A023196).
LINKS
FORMULA
a(n) = Sum_{d|n, d<n} A294936(d)*d. - Typo in A-number corrected by Antti Karttunen, Apr 04 2022
EXAMPLE
Proper divisors of 90 are 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, and 45. Of these 6, 18 and 30 are in A023196, thus a(90) = 6+18+30 = 54.
MATHEMATICA
a[n_] := DivisorSum[n, # &, # < n && DivisorSigma[1, #] >= 2*# &]; Array[a, 100] (* Amiram Eldar, Mar 14 2024 *)
PROG
(PARI) A294887(n) = sumdiv(n, d, (d<n)*(sigma(d)>=(2*d))*d);
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Nov 14 2017
STATUS
approved