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 A283454 #27 Feb 12 2021 04:07:15
%S A283454 2,2,11,2,2,2,2,2,11,2,2,2,2,2,11,2,2,2,2,2,11,2,2,13,2,2,2,11,2,2,2,
%T A283454 2,2,11,2,2,2,2,2,11,2,2,2,2,2,11,2,2,2,2,2,11,2,2,2,2,2,11,2,2,2,2,2,
%U A283454 11,2,2,2,2,2,11,2,13,2,2,2,2,11,2,2,2,2,2,11
%N A283454 The square root of the smallest square referenced in A249025 (Numbers k such that 3^k - 1 is not squarefree).
%C A283454 The terms are the smallest prime whose square divides 3^k-1, when it is not squarefree.
%H A283454 Amiram Eldar, <a href="/A283454/b283454.txt">Table of n, a(n) for n = 1..407</a> (terms 1..121 from Michel Marcus)
%F A283454 a(n) = A249739(A024023(A249025(n))). - _Amiram Eldar_, Feb 12 2021
%e A283454 A249025(3)=5, 3^5-1 = 242 = 2*11*11. 242 is not squarefree the square being 11*11 = 121, the root being 11.
%t A283454 p[n_] := If[(f = Select[FactorInteger[n], Last[#] > 1 &]) == {}, 1, f[[1, 1]]]; p /@ Select[3^Range[100] - 1, !SquareFreeQ[#] &] (* _Amiram Eldar_, Feb 12 2021 *)
%o A283454 (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], ", ");););} \\ _Michel Marcus_, Mar 11 2017
%Y A283454 Cf. A024023, A046027, A249025, A249739, A283453.
%K A283454 nonn
%O A283454 1,1
%A A283454 _Robert Price_, Mar 07 2017
%E A283454 More terms from _Michel Marcus_, Mar 11 2017