OFFSET
1,2
EXAMPLE
sigma(15) * antisigma(15) = 24 * 96 = 48^2, so 15 is a term of the sequence.
MATHEMATICA
l = {}; Do[s = DivisorSigma[1, n]; a = (n (n + 1)/2) - s; If[IntegerQ[Sqrt[a*s]], l = Append[l, n]], {n, 1, 10^5}]; l
CROSSREFS
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Oct 23 2002
EXTENSIONS
a(10) from Donovan Johnson, Jan 18 2012
STATUS
approved