OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harvey P. Dale)
EXAMPLE
x=30: sigma(30)=72, sigma(31)=32, product = 72*32 = 256*9 = 24^2.
MATHEMATICA
Do[s=Sqrt[DivisorSigma[1, n+1]*DivisorSigma[1, n]]; If[IntegerQ[s], Print[n]], {n, 1, 5000}]
Flatten[Position[Times@@@Partition[DivisorSigma[1, Range[5000]], 2, 1], _?(IntegerQ[Sqrt[#]]&)]] (* Harvey P. Dale, Mar 07 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, May 21 2003
STATUS
approved