A054017 Chowla's function of n modulo n is a square (excluding 0's).

14, 20, 39, 40, 46, 55, 80, 94, 100, 104, 117, 130, 155, 158, 183, 190, 200, 203, 291, 292, 295, 299, 320, 323, 334, 416, 430, 446, 464, 475, 488, 530, 539, 549, 567, 579, 583, 638, 650, 695, 718, 799, 873, 878, 890, 943, 955, 959, 964, 979, 1030, 1118

Offset: 1

Author

Asher Auel, Jan 19 2000

Keywords

• nonn

Comments

Chowla's function (A048050) = sum of divisors of n except 1 and n.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A048050, A054013, A054018.

Programs

Mathematica

aQ[n_] := (c = DivisorSigma[1, n] - n - 1) > 0 && IntegerQ @ Sqrt @ Mod[c, n]; Select[Range[1000], aQ] (* Amiram Eldar, Aug 28 2019 *)