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 A257572 #10 Apr 14 2025 05:32:35
%S A257572 2,2,2,3,2,2,3,2,3,2,2,3,2,2,3,5,2,3,2,5,2,3,2,3,2,5,2,3,2,5,2,3,7,2,
%T A257572 3,5,2,2,3,7,2,5,3,2,2,7,3,5,2,3,2,5,2,7,3,2,2,3,5,7,2,3,2,5,2,3,7,2,
%U A257572 5,3,2,2,3,7,2,5,2,3,11,2,7,5,3,2,2,3
%N A257572 Prime root of n-th term in A257278.
%H A257572 Reinhard Zumkeller, <a href="/A257572/b257572.txt">Table of n, a(n) for n = 1..10000</a>
%F A257572 a(n) = A020639(A257278(n)).
%F A257572 A257278(n) = a(n) ^ A257573(n).
%F A257572 a(n) <= A257573(n) by definition of A257278.
%t A257572 seq[lim_] := Module[{s = {}, p = 2, r}, While[p^p <= lim, r = Range[p, Log[p, lim]]; AppendTo[s, Transpose[{ConstantArray[p, Length[r]], p^r}]]; p = NextPrime[p]]; SortBy[Flatten[s, 1], Last][[;; , 1]]]; seq[10^13] (* _Amiram Eldar_, Apr 14 2025 *)
%o A257572 (Haskell)
%o A257572 a257572 = a020639 . a257278
%Y A257572 Cf. A257278, A020639, A025473, A257573.
%K A257572 nonn
%O A257572 1,1
%A A257572 _Reinhard Zumkeller_, May 01 2015