A068355 - OEIS

%I #13 May 11 2023 18:31:27

%S 45,105,135,165,195,225,315,405,495,525,567,585,675,693,735,765,819,

%T 825,855,945,975,1035,1071,1125,1155,1197,1215,1275,1287,1305,1323,

%U 1365,1395,1425,1449,1485,1575,1617,1665,1683,1701,1725,1755,1785,1815

%N Odd 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(n).

%t Select[Range[1,1901,2],DivisorSigma[1,#]DivisorSigma[0,#]>Prime[2#]&] (* _Harvey P. Dale_, Feb 17 2015 *)

%o (PARI) for(n=1,2200, if(sigma(n)*numdiv(n)*(1-(-1)^n)/2>prime(2*n),print1(n,",")))

%Y Cf. A000005.

%K easy,nonn

%O 1,1

%A _Benoit Cloitre_, Feb 28 2002