A160320 Numbers n for which sigma(n)/n = k+1/3 with integer k.

3, 12, 234, 1080, 6048, 6552, 435708, 4713984, 18506880, 36197280, 275890944, 299980800, 4138364160, 13286744064, 17827568640, 30600708096, 459010621440, 2198278051200, 2567400675840, 3321402084000, 4959751305600, 295185198672000, 1217745604232064

Offset: 1

Author

J.C. Klein (hklein(AT)planet.nl), May 08 2009

Keywords

• nonn

Examples

			a(1)=3 since sigma(3)/3=(1+3)/3=1+1/3.
a(2)=12 since sigma(12)/12=(1+2+3+4+6+12)/12=28/12=7/3=2+1/3.
		

Crossrefs

Cf. A160321 (sigma(n)/n=k+2/3), A159907 (sigma(n)/n=k+1/2).

Programs

PARI

is(n)=denominator(sigma(n,-1)-1/3)==1 \\ Charles R Greathouse IV, Mar 09 2014

Extensions

a(11)-a(16) from Donovan Johnson, May 26 2009

a(17)-a(23) from Michel Marcus, Sep 21 2012