|
|
A221285
|
|
Square values taken by totient function phi(m) = A000010(m).
|
|
7
|
|
|
1, 4, 16, 36, 64, 100, 144, 196, 256, 324, 400, 576, 676, 784, 900, 1024, 1296, 1600, 1764, 1936, 2304, 2500, 2704, 2916, 3136, 3600, 4096, 4356, 4624, 4900, 5184, 5476, 6400, 7056, 7744, 8100, 8836, 9216, 10000, 10816, 11664, 12100, 12544, 12996, 13456, 14400, 15376, 15876
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
LINKS
|
|
|
FORMULA
|
Pollack & Pomerance show that n^2 log^.0126 n << a(n) << n^2 log^6 n.
|
|
MATHEMATICA
|
inversePhiSingle[(m_)?EvenQ] := Module[{p, nmax, n}, p = Select[Divisors[m] + 1, PrimeQ]; nmax = m*Times @@ (p/(p - 1)); n = m; While[n <= nmax, If[EulerPhi[n] == m, Return[n]]; n++]; 0];
Reap[For[k = 1, k <= 200, k = k + If[k==1, 1, 2], If[inversePhiSingle[k^2] > 0, Print[k^2]; Sow[k^2]]]][[2, 1]] (* Jean-François Alcover, Dec 11 2018 *)
|
|
PROG
|
(PARI) is(n)=issquare(n) && istotient(n)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|