A054018 - OEIS

A054018

Squares mentioned in A054017.

9, 1, 16, 9, 25, 16, 25, 49, 16, 1, 64, 121, 36, 81, 64, 169, 64, 36, 100, 225, 64, 36, 121, 36, 169, 49, 361, 225, 1, 144, 441, 441, 144, 256, 400, 196, 64, 441, 1, 144, 361, 64, 400, 441, 729, 64, 196, 144, 729, 100, 841, 729, 25, 400, 256, 1225, 100, 729, 1225

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OFFSET

1,1

COMMENTS

If Chowla's function of n read (modulo n) is a nonzero square, print this square.

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

MATHEMATICA

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

CROSSREFS

Cf. A048050, A054013, A054017, A054019.

Sequence in context: A145966 A349143 A014721 * A342637 A010170 A317051

Adjacent sequences: A054015 A054016 A054017 * A054019 A054020 A054021

KEYWORD

nonn

AUTHOR

Asher Auel, Jan 19 2000

STATUS

approved