A068354 Numbers n such that sigma(n)*tau(n) > prime(2*n) where sigma(n) is the sum of divisors of n and tau(n) the number of divisors of n (A000005).

4, 6, 8, 10, 12, 16, 18, 20, 24, 28, 30, 32, 36, 40, 42, 44, 45, 48, 50, 52, 54, 56, 60, 64, 66, 70, 72, 78, 80, 84, 88, 90, 96, 100, 102, 104, 105, 108, 110, 112, 114, 120, 126, 128, 130, 132, 135, 136, 138, 140, 144, 150, 152, 154, 156, 160, 162, 165, 168, 170

Offset: 1

Author

Benoit Cloitre, Feb 28 2002

Keywords

• easy
• nonn

Crossrefs

Cf. A000005, A000203, A031215, A064840.

Programs

Mathematica

Select[Range[200],DivisorSigma[0,#]DivisorSigma[1,#]>Prime[2#]&] (* Harvey P. Dale, Aug 15 2011 *)

PARI

for(n=1,1000, if(sigma(n)*numdiv(n)>prime(2*n),print1(n,",")))