OFFSET
1,2
COMMENTS
If m belongs to the sequence, then sigma(2*m)/m is an integer, so sigma(2*m)/(2*m) is either an integer or half of an integer, so 2*m is either perfect, multiperfect or hemiperfect. - Michel Marcus, Jul 09 2013
LINKS
Jinyuan Wang, Table of n, a(n) for n = 1..54
PROG
(PARI) is(n)=sigma(2*n)%n==0 \\ Charles R Greathouse IV, Nov 04 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Jul 05 2013
STATUS
approved