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 A300518 #31 Oct 28 2024 09:35:51
%S A300518 1,2,3,1,5,3,7,2,1,5,11,3,13,7,5,1,17,2,19,5,7,11,23,3,1,13,3,7,29,5,
%T A300518 31,2,11,17,7,1,37,19,13,5,41,7,43,11,5,23,47,3,1,2,17,13,53,3,11,7,
%U A300518 19,29,59,5,61,31,7,1,13,11,67,17,23,7,71,2,73,37
%N A300518 The greatest prime factor of the squarefree part of n, or 1 if n is square.
%C A300518 The greatest prime factor of n that has an odd exponent in the prime factorization of n, or 1 is no such prime exists. - _Amiram Eldar_, Oct 28 2024
%H A300518 Alois P. Heinz, <a href="/A300518/b300518.txt">Table of n, a(n) for n = 1..20000</a>
%H A300518 Hugo Pfoertner, <a href="/A300518/a300518.pdf">Illustration of first 10^5 terms</a>, zoom into central part to see nice patterns.
%F A300518 a(n) = A006530(A007913(n)).
%e A300518 For n = 15000 = 5^4 * 3 * 2^3, 3 is the greatest unpaired prime, so a(15000) = 3.
%p A300518 a:= n-> max(1, seq(i[1]^irem(i[2], 2), i=ifactors(n)[2])):
%p A300518 seq(a(n), n=1..100); # _Alois P. Heinz_, Mar 07 2018
%t A300518 Array[FactorInteger[Sqrt[#] /. (c_: 1)*a_^(b_: 0) :> (c*a^b)^2][[-1, 1]] &, 74] (* _Michael De Vlieger_, Mar 10 2018, after _Bill Gosper_ at A007913 *)
%o A300518 (PARI) gpf(n) = if (n==1, 1, vecmax(factor(n)[,1]));
%o A300518 a(n) = gpf(core(n)); \\ _Michel Marcus_, Mar 08 2018
%o A300518 (PARI) a(n) = {my(f = factor(n)); forstep(i = #f~, 1, -1, if(f[i,2] % 2, return(f[i, 1]))); 1;} \\ _Amiram Eldar_, Oct 28 2024
%o A300518 (Magma) [#f eq 0 select 1 else f[#f][1] where f is Factorization(Squarefree(n)): n in [1..90]]; // _Vincenzo Librandi_, Mar 08 2018
%Y A300518 Cf. A006530, A007913.
%K A300518 nonn,easy
%O A300518 1,2
%A A300518 _Peter Kagey_, Mar 07 2018