OFFSET
1,1
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..1000
MATHEMATICA
Do[ s=DivisorSigma[ 0, n^2 ]; y=DivisorSigma[ 1, n^2 ]; If[ Equal[ Length[ FactorInteger[ n ] ], 1 ]&&!PrimeQ[ n ] &&!PrimeQ[ s ]&&!PrimeQ[ y ], Print[ n ] ], {n, 1, 10000000} ]
Select[Range[16778000], PrimePowerQ[#]&&AllTrue[{DivisorSigma[ 0, #^2], DivisorSigma[ 1, #^2]}, CompositeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 18 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 19 2001
STATUS
approved