|
|
A152215
|
|
Numbers k such that sigma_2(k)/(sigma_1(k)*sigma_0(k)) = c, c an integer.
|
|
1
|
|
|
1, 4, 25, 100, 121, 256, 289, 484, 529, 841, 1156, 1600, 1681, 2116, 2209, 2809, 3025, 3364, 3481, 5041, 6400, 6724, 6889, 7225, 7921, 8836, 10201, 11236, 11449, 12100, 12769, 13225, 13924, 17161, 18225, 18496, 18769, 20164, 21025, 22201, 27556, 27889, 28900
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
|
|
LINKS
|
|
|
MATHEMATICA
|
Select[Range[50000], IntegerQ[DivisorSigma[2, #]/(DivisorSigma[1, #] DivisorSigma[ 0, #])]&] (* Harvey P. Dale, Feb 12 2013 *)
|
|
PROG
|
(PARI) isok(k) = denominator(sigma(k, 2)/(sigma(k, 1)*sigma(k, 0))) == 1; \\ Michel Marcus, Jul 15 2019
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|