This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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, 227917248343616414016, 79758963630439261338240, 413838290195487519174516, 638755027963568013738240 (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 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 Cf. A000203, A024916, A168127, A168128, A168129. Sequence in context: A199801 A278857 A202910 * A270871 A037076 A116245 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 a(11)-a(14) from Giovanni Resta, Jun 06 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 20 15:29 EDT 2019. Contains 328267 sequences. (Running on oeis4.)