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A341620 Number of nondeficient divisors of n. 6
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

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for sequences related to sigma(n)

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

Cf. A000005, A006039 (positions of ones), A023196, A080224, A080225, A080226, A294927, A294936, A337690, A341619.

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

Adjacent sequences:  A341617 A341618 A341619 * A341621 A341622 A341623

KEYWORD

nonn

AUTHOR

Antti Karttunen, Feb 21 2021

STATUS

approved

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Last modified May 22 05:51 EDT 2022. Contains 353933 sequences. (Running on oeis4.)