A122906 Numbers m such that in Z/mZ the number of squares is less than or equal to the number of invertible elements.

1, 3, 4, 5, 7, 8, 9, 11, 12, 13, 15, 16, 17, 19, 20, 21, 23, 24, 25, 27, 28, 29, 31, 32, 33, 35, 36, 37, 39, 40, 41, 43, 44, 45, 47, 48, 49, 51, 52, 53, 55, 56, 57, 59, 60, 61, 63, 64, 65, 67, 68, 69, 70, 71, 72, 73, 75, 76, 77, 79, 80, 81, 83, 84, 85, 87, 88, 89, 90, 91, 92, 93

Offset: 1

Author

Max Alekseyev, Sep 18 2006

Keywords

• nonn

Comments

Numbers m such that A000224(m) <= A000010(m).

The terms 70 and 90 show that sequence is strictly different from A042965. - Andrew S. Plewe, Jun 13 2007

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000

Crossrefs

Union of A122903 and A122904.

Complement of A122905 in positive integers.

Cf. A000010, A000224, A122907.

Programs

Mathematica

Select[Range@94, Length@Union@Mod[Range[#]^2, #] <= EulerPhi[#] &] (* Ivan Neretin, Dec 14 2016 *)
f1[p_, e_] := Floor[p^(e+1)/(2p + 2)] + 1; f1[2, e_] := Floor[2^e/6] + 2; f[p_, e_] := f1[p, e]/((p-1) * p^(e-1)); q[1] = True; q[k_] := Times @@ f @@@ FactorInteger[k] <= 1; Select[Range[100], q] (* Amiram Eldar, Nov 11 2024 *)