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A177012 Numbers k such that k^k == -1 (mod phi(k)). 1
1, 2, 3, 15, 87, 255, 11759, 26279, 39455, 43919, 65535, 112895, 443807, 1347455, 1464911, 1568255, 1604559, 1968095, 2441559, 5948799, 16210655, 39624767, 39839039, 59187455, 81624279, 83623935, 251009695, 256685439, 338979839, 434357967, 455345855, 471783935, 487722815, 518291135, 596835839 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
3 is the largest prime term of this sequence.
All terms are squarefree. There is no further term up to 2*10^8.
If phi(k) divides k+1 then k is in the sequence. This implies A050474 and A203966 are subsequences of this sequence. - Jahangeer Kholdi, Dec 10 2014
LINKS
EXAMPLE
phi(15)=8 and 15^15 == -1 (mod 8), so 15 is in the sequence.
MATHEMATICA
v={}; Do[If[PowerMod[n, n, EulerPhi[n]]==EulerPhi[n]-1, AppendTo[v, n];
Print[v]], {n, 200000000}]
CROSSREFS
Sequence in context: A047014 A027519 A245107 * A107413 A358119 A238711
KEYWORD
nonn
AUTHOR
Farideh Firoozbakht, May 19 2010
EXTENSIONS
a(27)-a(29) from Jahangeer Kholdi, Dec 10 2014
a(30)-a(35) from Farideh Firoozbakht, Dec 10 2014
STATUS
approved

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Last modified March 29 09:14 EDT 2024. Contains 371268 sequences. (Running on oeis4.)