A168128 Numbers Sum_(j=1..k) sigma(j) / sigma(k) when this expression is an integer.

1, 2, 23, 247, 699, 55921, 70936, 152730, 478017, 4879815, 12909834588, 223070292558, 583407686653, 601718433498

Offset: 1

Author

Jaroslav Krizek, Nov 18 2009, Dec 04 2009

Keywords

• nonn
• more

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

Examples

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

Crossrefs

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

Programs

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

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