OFFSET
1,2
EXAMPLE
sigma(90)^2 - 90^2 = 234^2 - 90^2 = 216^2, so 90 is a term of the sequence.
MATHEMATICA
Select[ Range[ 1, 10^6 ], IntegerQ[ Sqrt[ DivisorSigma[ 1, # ]^2 - #^2 ] ] & ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Jan 18 2002
EXTENSIONS
a(7)-a(10) from Sean A. Irvine, Nov 06 2023
a(11)-a(23) from Martin Ehrenstein, Jul 12 2024
STATUS
approved