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A285896 Sum of divisors d of n such that n/d is not congruent to 0 mod 5. 5
1, 3, 4, 7, 5, 12, 8, 15, 13, 15, 12, 28, 14, 24, 20, 31, 18, 39, 20, 35, 32, 36, 24, 60, 25, 42, 40, 56, 30, 60, 32, 63, 48, 54, 40, 91, 38, 60, 56, 75, 42, 96, 44, 84, 65, 72, 48, 124, 57, 75, 72, 98, 54, 120, 60, 120, 80, 90, 60, 140, 62, 96, 104, 127, 70, 144 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = (A000203(5*n)-A000203(n))/5.

G.f.: Sum_{k>=1} k*x^k*(1 + x^k + x^(2*k) + x^(3*k))/(1 - x^(5*k)). - Ilya Gutkovskiy, Sep 12 2019

EXAMPLE

The divisors of 10 are 1, 2, 5, and 10. 10/1 == 0 (mod 5) and 10/2 == 0 (mod 5). Hence, a(10) = 5 + 10 = 15.

PROG

(PARI) a(n)=sumdiv(n, d, if(n/d%5, d, 0)); \\ Andrew Howroyd, Jul 20 2018

CROSSREFS

Cf. A002131 (k=2), A078708 (k=3), A285895 (k=4), this sequence (k=5).

Sequence in context: A338285 A050197 A003975 * A082226 A010613 A299693

Adjacent sequences:  A285893 A285894 A285895 * A285897 A285898 A285899

KEYWORD

nonn,mult

AUTHOR

Seiichi Manyama, Apr 28 2017

EXTENSIONS

Keyword:mult added by Andrew Howroyd, Jul 20 2018

STATUS

approved

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Last modified June 22 19:11 EDT 2021. Contains 345388 sequences. (Running on oeis4.)