cp's OEIS Frontend

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.

A375075 Numbers whose prime factorization exponents include at least one 1, at least one 2, at least one 3 and no other exponents.

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%I A375075 #6 Jul 30 2024 14:36:51
%S A375075 360,504,540,600,756,792,936,1176,1188,1224,1350,1368,1400,1404,1500,
%T A375075 1656,1836,1960,2052,2088,2200,2232,2250,2484,2520,2600,2646,2664,
%U A375075 2904,2952,3096,3132,3348,3384,3400,3500,3780,3800,3816,3960,3996,4056,4116,4200,4248,4312,4392,4428
%N A375075 Numbers whose prime factorization exponents include at least one 1, at least one 2, at least one 3 and no other exponents.
%C A375075 First differs from its subsequence A163569 at n = 25: a(25) = 2520 = 2^3 * 3^2 * 5 * 7 is not a term of A163569.
%C A375075 Numbers k such that the set of distinct prime factorization exponents of k (row k of A136568) is {1, 2, 3}.
%C A375075 The asymptotic densities of this sequence and A375074 are equal (0.0156712..., see A375074 for a formula), since the terms in A375074 that are not in this sequence (A375073) have a density 0.
%H A375075 Amiram Eldar, <a href="/A375075/b375075.txt">Table of n, a(n) for n = 1..10000</a>
%H A375075 <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a>.
%t A375075 Select[Range[4500], Union[FactorInteger[#][[;; , 2]]] == {1, 2, 3} &]
%o A375075 (PARI) is(k) = Set(factor(k)[,2]) == [1, 2, 3];
%Y A375075 Intersection of A375072 and A317090.
%Y A375075 Equals A375074 \ A375073.
%Y A375075 Subsequence of A046100 and A176297.
%Y A375075 A163569 is a subsequence.
%Y A375075 Cf. A002117, A013661, A013662, A013664, A059956, A068468, A088453, A136568, A215267.
%K A375075 nonn,easy
%O A375075 1,1
%A A375075 _Amiram Eldar_, Jul 29 2024