This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A054018 #11 Oct 27 2023 22:00:46 %S A054018 9,1,16,9,25,16,25,49,16,1,64,121,36,81,64,169,64,36,100,225,64,36, %T A054018 121,36,169,49,361,225,1,144,441,441,144,256,400,196,64,441,1,144,361, %U A054018 64,400,441,729,64,196,144,729,100,841,729,25,400,256,1225,100,729,1225 %N A054018 Squares mentioned in A054017. %C A054018 If Chowla's function of n read (modulo n) is a nonzero square, print this square. %C A054018 Chowla's function (A048050) = sum of divisors of n except 1 and n. %H A054018 Amiram Eldar, <a href="/A054018/b054018.txt">Table of n, a(n) for n = 1..10000</a> %t A054018 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 *) %Y A054018 Cf. A048050, A054013, A054017, A054019. %K A054018 nonn %O A054018 1,1 %A A054018 _Asher Auel_, Jan 19 2000