A227302 Numbers m such that m divides sigma(2*m).

1, 3, 12, 14, 60, 248, 336, 2160, 2340, 4064, 13104, 15120, 16380, 261888, 1089270, 4455360, 8714160, 10213632, 11784960, 16775168, 22766400, 45981824, 71495424, 98532480, 229909120, 689727360, 738152448, 4291822080, 4294934528, 5100118016, 7091219520

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

Cf. A000203, A000396, A007691, A159907, A232702.

Cf. A141643, A055153, A141645, A159271, A160678. (hemiperfect numbers)

Sequence in context: A286386 A032918 A039945 * A201273 A221920 A349663

Adjacent sequences: A227299 A227300 A227301 * A227303 A227304 A227305

Keyword

nonn

Author

Alex Ratushnyak, Jul 05 2013

Status

approved