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A168128 Numbers Sum_(j=1..k) sigma(j) / sigma(k) when this expression is an integer. 3
1, 2, 23, 247, 699, 55921, 70936, 152730, 478017, 4879815, 12909834588, 223070292558, 583407686653, 601718433498 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers A024916(k)/A000203(k) when it is an integer.

Corresponding values of k, sigma(k) and Sum_(j=1..k) sigma(j) are given in A168127, A168129 and A168130. - Jaroslav Krizek, Nov 21 2009

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

a(3)=23 because A024916(29) / A000203(29) = 690 / 30 = 23 is an integer, where 29 is A168127(3).

PROG

(PARI) m=0; for(k=1, 11413204, s=sigma(k); m=m+s; if(m%s==0, print1(m/s ", "))) \\ Donovan Johnson, Oct 16 2013

CROSSREFS

Cf. A000203, A024916, A168127, A168129, A168130.

Sequence in context: A088087 A088085 A309221 * A233783 A300326 A068983

Adjacent sequences:  A168125 A168126 A168127 * A168129 A168130 A168131

KEYWORD

nonn,more

AUTHOR

Jaroslav Krizek, Nov 18 2009, Dec 04 2009

EXTENSIONS

a(8)-a(10) from Donovan Johnson, Oct 16 2013

a(11)-a(14) from Giovanni Resta, Jun 06 2016

Name edited by Michel Marcus, Feb 22 2020

STATUS

approved

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Last modified September 26 13:58 EDT 2022. Contains 356998 sequences. (Running on oeis4.)