|
|
A050934
|
|
Numbers k such that phi(k)*d(k) is a multiple of sigma(k), where d(k) is the number of divisors of k.
|
|
1
|
|
|
1, 3, 14, 35, 42, 105, 209, 248, 297, 418, 594, 627, 744, 1045, 1254, 1485, 1736, 2926, 3135, 3339, 3596, 3689, 3956, 4064, 4158, 5208, 5396, 5890, 6461, 7315, 7668, 8370, 8636, 8680, 8778, 8932, 9875, 10013, 10395, 10788, 11067, 11687
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
Equality holds for 1, 3, 14, 42 and no others < 4290000000.
|
|
LINKS
|
|
|
EXAMPLE
|
phi(35)*d(35) = 4*24, a multiple of sigma(35) = 48, so 35 is in the sequence.
|
|
MATHEMATICA
|
Select[Range[12000], Divisible[EulerPhi[#]DivisorSigma[0, #], DivisorSigma[ 1, #]]&] (* Harvey P. Dale, Jan 11 2019 *)
|
|
PROG
|
(PARI) is(n) = {my(f = factor(n)); !((eulerphi(f) * numdiv(f)) % sigma(f)); } \\ Amiram Eldar, Apr 04 2024
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|