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 A283453 #15 Feb 12 2021 04:06:26
%S A283453 4,4,121,4,4,4,4,4,121,4,4,4,4,4,121,4,4,4,4,4,121,4,4,169,4,4,4,121,
%T A283453 4,4,4,4,4,121,4,4,4,4,4,121,4,4,4,4,4,121,4,4,4,4,4,121,4,4,4,4,4,
%U A283453 121,4,4,4,4,4,121,4,4,4,4,4,121,4,169,4,4,4,4,121
%N A283453 The smallest square referenced in A249025 (Numbers k such that 3^k - 1 is not squarefree).
%H A283453 Amiram Eldar, <a href="/A283453/b283453.txt">Table of n, a(n) for n = 1..407</a>
%F A283453 a(n) = A283454(n)^2. - _Amiram Eldar_, Feb 12 2021
%e A283453 A249025(3)=5, 3^5-1 = 242 = 2*11*11. 242 is not squarefree the square being 11*11 = 121.
%t A283453 psq[n_] := If[(f = Select[FactorInteger[n], Last[#] > 1 &]) == {}, 1, f[[1, 1]]^2]; psq /@ Select[3^Range[100] - 1, !SquareFreeQ[#] &] (* _Amiram Eldar_, Feb 12 2021 *)
%o A283453 (PARI) lista(nn) = {for (n=1, nn, if (!issquarefree(k = 3^n-1), f = factor(k/core(k)); vsq = select(x->((x%2) == 0), f[,2], 1); print1(f[vsq[1], 1]^2, ", ");););} \\ _Michel Marcus_, Mar 11 2017
%Y A283453 Cf. A249025, A283454.
%K A283453 nonn
%O A283453 1,1
%A A283453 _Robert Price_, Mar 07 2017
%E A283453 More terms from _Michel Marcus_, Mar 11 2017