|
|
A015796
|
|
Numbers k such that phi(k) + 5 | sigma(k).
|
|
0
|
|
|
4, 10, 32, 60, 88, 688, 2544, 3424, 12200, 62848, 777984, 1037824, 16734208, 67022848, 8625555968, 51537444864, 1099500617728
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
a(18) <= 17592142004224. In general, if 2^k-11 is prime (A096817) then 2^(k-2)*3*(2^k-11) is a term for k > 3. Moreover, if 2^k-21 is prime (A096820) then 2^(k-2)*(2^k-21) is a term for k > 4. - Giovanni Resta, Sep 09 2019
|
|
LINKS
|
|
|
MATHEMATICA
|
Select[Range[100000],
Divisible[DivisorSigma[1, #], EulerPhi[#] + 5] &] (* David Nacin, Feb 28 2012 *)
|
|
CROSSREFS
|
Cf. A000010, A000203, A056097, A015812, A015792, A015793, A015797, A015798, A015799, A015800, A015801, A015804, A015805, A096817, A096820.
|
|
KEYWORD
|
nonn,more
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|