OFFSET
1,1
COMMENTS
Note that numbers which are an integral multiple of the sum of their proper divisors excluding 1 (A048050) are the squares of primes (A001248).
Subsequence of A166070. - Jaroslav Krizek, Oct 06 2009
MAPLE
isA053813 := proc(n) add(1/j, j=numtheory:-divisors(n)): numer(%) = denom(%) + 1 end: select(isA053813, [$1..271]); # Peter Luschny, Oct 03 2018
MATHEMATICA
Select[Range[300], PrimeQ[#] || DivisorSigma[1, #] == 2*#&] (* Jean-François Alcover, Jun 03 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Henry Bottomley, Mar 28 2000
STATUS
approved