|
Search: id:A066782
|
|
|
| A066782 |
|
Numbers n such that (n,EulerPhi(n)) lies on the hyperbola x^2 - y^2 = m^2, for some natural number m, i.e. n^2 - EulerPhi(n)^2 = m^2. |
|
+0
1
|
|
| 1, 5, 13, 25, 34, 41, 61, 68, 113, 125, 136, 169, 181, 219, 222, 272, 313, 390, 421, 444, 482, 544, 578, 613, 625, 657, 666, 761, 780, 888, 964, 979, 1013, 1088, 1156, 1170, 1201, 1301, 1332, 1560, 1681, 1741, 1776, 1861
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
EXAMPLE
|
5^2 - EulerPhi(5)^2 = 25 - 16 = 3^2, so 5 is a term of the sequence.
|
|
MATHEMATICA
|
Select[ Range[ 1, 10^4 ], IntegerQ[ Sqrt[ #^2 - EulerPhi[ # ]^2 ] ] & ]
|
|
CROSSREFS
|
Adjacent sequences: A066779 A066780 A066781 this_sequence A066783 A066784 A066785
Sequence in context: A140090 A121511 A004627 this_sequence A094553 A094079 A112558
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jan 18 2002
|
|
|
Search completed in 0.002 seconds
|
