

A175874


a(n) = least number such that sigma(a(n)+n)=n*sigma(a(n)).


2




OFFSET

1,1


COMMENTS

a(1)= A002961(1).
a(2)= A175876(1), a(3)= A175875(1).  Zak Seidov, Jul 07 2013
Is n = 2 the only solution for sigma(n+4)=4*sigma(n)?  Zak Seidov, Jul 07 2013
A further solution to sigma(n+4)=4*sigma(n), and the terms a(5) and a(6), if they exist, they are all larger than 3*10^12.  Giovanni Resta, Jun 06 2016


LINKS

Table of n, a(n) for n=1..4.


EXAMPLE

sigma(14+1)/sigma(14)=24/24=1, sigma(118+2)/sigma(118)=360/180=2,
sigma(3+3)/sigma(3)=12/4=3, sigma(4+4)/sigma(2)=12/3=4.


CROSSREFS

Cf. A000203 sigma(n), A002961 sigma(n) = sigma(n+1).
Cf. A175875, A175876.  Zak Seidov, Jul 07 2013
Sequence in context: A279855 A128569 A138431 * A006223 A091303 A241463
Adjacent sequences: A175871 A175872 A175873 * A175875 A175876 A175877


KEYWORD

more,nonn


AUTHOR

Zak Seidov, Oct 06 2010


STATUS

approved



