|
|
A067798
|
|
Numbers n such that phi(n)+phi(n+1)=n+1.
|
|
1
|
|
|
1, 2, 3, 5, 9, 15, 21, 35, 39, 45, 75, 99, 135, 231, 255, 363, 483, 765, 855, 1295, 1599, 2015, 2115, 4335, 6783, 9999, 14399, 16095, 16599, 18495, 30495, 53823, 62799, 63455, 65535, 77615, 155319, 186999, 196095, 327675, 589815, 686735, 722015
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
|
|
MATHEMATICA
|
Select[Range[10^5], Plus @@ EulerPhi[{#, # + 1}] == # + 1 &] (* Giovanni Resta, May 15 2016 *)
|
|
PROG
|
(PARI) isok(n) = eulerphi(n)+eulerphi(n+1) == n+1; \\ Michel Marcus, May 15 2016
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|