A114080 Numbers k such that sigma(k) times the k-th prime is a brilliant number (A078972).

2, 4, 9, 16, 25, 64, 729, 65536

Offset: 1

Author

Giovanni Resta, Feb 13 2006

Keywords

• nonn
• base

Comments

No additional terms up to 1 million. - Harvey P. Dale, Nov 13 2013

Examples

			sigma(25) * p(25) = 3007 = 31*97.
		

Programs

Mathematica

brilQ[n_]:=Module[{pf=Transpose[FactorInteger[n]][[1]]},PrimeOmega[n] == 2&&IntegerLength[First[pf]]==IntegerLength[Last[pf]]]; Select[Range[ 100000], brilQ[DivisorSigma[1,#]Prime[#]]&] (* Harvey P. Dale, Nov 13 2013 *)