A168130 Numbers Sum_(j=1..k) sigma(j) when Sum_(j=1..k) sigma(j) / sigma(k) is an integer.

1, 8, 690, 109668, 1235133, 5475784320, 6118230000, 28361961000, 279467858880, 107135567314230, 227917248343616414016, 79758963630439261338240, 413838290195487519174516, 638755027963568013738240

Offset: 1

Author

Jaroslav Krizek, Nov 18 2009, Dec 04 2009

Keywords

• nonn
• more

Comments

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

Corresponding values of k, sigma(k), and Sum_(j=1..k) sigma(j)/sigma(k) are given in A168127, A168129, and A168128. - Jaroslav Krizek, Nov 21 2009

Examples

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

Crossrefs

Cf. A000203, A024916, A168127, A168128, A168129.

Programs

PARI

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

Formula

a(n) = A024916(A168127(n)). - Michel Marcus, Feb 22 2020

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