|
| |
|
|
A173703
|
|
Composite numbers n with the property that phi(n) divides (n-1)^2.
|
|
2
|
|
|
|
561, 1105, 1729, 2465, 6601, 8481, 12801, 15841, 16705, 19345, 22321, 30889, 41041, 46657, 50881, 52633, 71905, 75361, 88561, 93961, 115921, 126673, 162401, 172081, 193249, 247105, 334153, 340561, 378561, 449065, 460801, 574561, 656601, 658801, 670033
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
REFERENCES
|
J. M. Grau and A. M. Oller-Marcen, On k-Lehmer Numbers, Integers, 12 (2012), #A37. - From N. J. A. Sloane, Dec 21 2012
|
|
|
LINKS
|
Joerg Arndt, Table of n, a(n) for n = 1..327 (all terms <= 10^9).
|
|
|
EXAMPLE
|
a(1) = 561 is in the sequence because 560^2 = phi(561)*980 = 320*980 = 313600.
|
|
|
MATHEMATICA
|
Table[If[PrimeQ[n]===False&&IntegerQ[(n-1)^2/EulerPhi[n]], n], {n, 3, 100000}]//Union
|
|
|
PROG
|
(PARI)
N=10^9;
default(primelimit, N);
ct = 0;
{ for (n=4, N,
if ( ! isprime(n),
if ( ( (n-1)^2 % eulerphi(n) ) == 0,
ct += 1;
print(ct, " ", n);
);
);
); }
/* Joerg Arndt, Jun 23 2012 */
|
|
|
CROSSREFS
|
Cf. A000010, A207080.
Sequence in context: A104016 A002997 A087788 * A083733 A214428 A175737
Adjacent sequences: A173700 A173701 A173702 * A173704 A173705 A173706
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
José María Grau Ribas, Nov 25 2010
|
|
|
STATUS
|
approved
|
| |
|
|
