OFFSET
1,2
COMMENTS
Numbers k such that sigma(k) is divisible by all proper divisors of k.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
EXAMPLE
a(4) = 6: all proper divisors of 6 (1, 2, 3) divide sigma(6) = 12.
MATHEMATICA
Select[Range[300], And@@Divisible[DivisorSigma[1, #], Most[Divisors[#]]]&] (* Harvey P. Dale, Jan 18 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Oct 06 2009, Oct 16 2009
STATUS
approved