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A168130 Numbers m = sum_(k=1...n) sigma(k) such that sum_(k=1...n) sigma(k) / sigma (k) is an integer for any k. 3
1, 8, 690, 109668, 1235133, 5475784320, 6118230000, 28361961000, 279467858880, 107135567314230 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Numbers m = A024916(k) such that A024916(k) / A000203(k) is an integer for any k.

Corresponding values of k, sigma (k), and sum_(k=1...n) sigma(k)/sigma(k) are given in A168127, A168129, and A168128. [Jaroslav Krizek, Nov 21 2009]

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

Number a(3) = 690 = A024916(29) is in sequence because A024916(29) / A000203(29) = 690 / 30 = 23 is an integer for k = 29.

PROG

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

CROSSREFS

Sequence in context: A128875 A199801 A202910 * A037076 A116245 A221198

Adjacent sequences:  A168127 A168128 A168129 * A168131 A168132 A168133

KEYWORD

nonn,more

AUTHOR

Jaroslav Krizek, Nov 18 2009, Dec 04 2009

EXTENSIONS

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

STATUS

approved

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Last modified November 26 07:08 EST 2014. Contains 250020 sequences.