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A341620 Number of nondeficient divisors of n. 8
0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 2, 0, 1, 0, 0, 0, 3, 0, 0, 0, 1, 0, 2, 0, 0, 0, 0, 0, 4, 0, 0, 0, 2, 0, 2, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 3, 0, 2, 0, 0, 0, 5, 0, 0, 0, 0, 0, 2, 0, 0, 0, 1, 0, 6, 0, 0, 0, 0, 0, 2, 0, 3, 0, 0, 0, 5, 0, 0, 0, 1, 0, 4, 0, 0, 0, 0, 0, 5, 0, 0, 0, 2, 0, 2, 0, 1, 0, 0, 0, 6, 0, 0, 0, 3, 0, 2, 0, 0, 0, 0, 0, 8 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,12
COMMENTS
Number of nondeficient numbers (A023196) dividing n.
LINKS
FORMULA
a(n) = Sum_{d|n} A294936(d).
a(n) = A294927(n) + A294936(n).
a(n) = A080224(n) + A080225(n) = A000005(n) - A080226(n).
a(n) >= A337690(n) for all n.
a(n) = 1 iff A341619(n) = 1.
MATHEMATICA
a[n_] := DivisorSum[n, 1 &, DivisorSigma[1, #] >= 2*# &]; Array[a, 120] (* Amiram Eldar, Feb 22 2021 *)
PROG
(PARI)
A294936(n) = (sigma(n, -1)>=2); \\ From A294936.
A341620(n) = sumdiv(n, d, A294936(d));
(PARI) A341620(n) = sumdiv(n, d, (sigma(d)>=(2*d)));
CROSSREFS
Differs from a derived sequence A341624 for the first time at n=120, where a(120)=8, while A341624(120)=1.
Sequence in context: A028649 A305558 A341624 * A097798 A065205 A036272
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 21 2021
STATUS
approved

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Last modified July 24 13:53 EDT 2024. Contains 374584 sequences. (Running on oeis4.)