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Numbers whose maximal exponent in their prime factorization is even.
13

%I #12 Sep 08 2024 17:11:17

%S 1,4,9,12,16,18,20,25,28,36,44,45,48,49,50,52,60,63,64,68,75,76,80,81,

%T 84,90,92,98,99,100,112,116,117,121,124,126,132,140,144,147,148,150,

%U 153,156,162,164,169,171,172,175,176,180,188,192,196,198,204,207,208

%N Numbers whose maximal exponent in their prime factorization is even.

%C First differs from A240112 at n = 30.

%C Numbers k such that A051903(k) is even.

%C The asymptotic density of this sequence is Sum_{k>=2} (-1)^k * (1 - 1/zeta(k)) = 0.27591672059822700769... .

%H Amiram Eldar, <a href="/A368714/b368714.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[Range[210], # == 1 || EvenQ[Max[FactorInteger[#][[;;, 2]]]] &]

%o (PARI) lista(kmax) = for(k = 1, kmax, if(k == 1 || !(vecmax(factor(k)[,2])%2), print1(k, ", ")));

%Y Cf. A051903, A240112.

%Y Subsequences: A000290, A000302, A000583, A001014, A001016, A001025, A008454, A062503, A067259.

%Y Similar sequences: A060476, A074661, A096432, A336064, A368715.

%K nonn,easy

%O 1,2

%A _Amiram Eldar_, Jan 04 2024