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A160320
Numbers n for which sigma(n)/n = k+1/3 with integer k.
11
3, 12, 234, 1080, 6048, 6552, 435708, 4713984, 18506880, 36197280, 275890944, 299980800, 4138364160, 13286744064, 17827568640, 30600708096, 459010621440, 2198278051200, 2567400675840, 3321402084000, 4959751305600, 295185198672000, 1217745604232064
OFFSET
1,1
EXAMPLE
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.
PROG
(PARI) is(n)=denominator(sigma(n, -1)-1/3)==1 \\ Charles R Greathouse IV, Mar 09 2014
CROSSREFS
Cf. A160321 (sigma(n)/n=k+2/3), A159907 (sigma(n)/n=k+1/2).
Sequence in context: A211892 A063801 A366504 * A321603 A297564 A280086
KEYWORD
nonn
AUTHOR
J.C. Klein (hklein(AT)planet.nl), May 08 2009
EXTENSIONS
a(11)-a(16) from Donovan Johnson, May 26 2009
a(17)-a(23) from Michel Marcus, Sep 21 2012
STATUS
approved