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 A375076 #10 Jul 30 2024 14:37:02 %S A375076 24,40,54,56,88,104,120,135,136,152,168,184,189,232,248,250,264,270, %T A375076 280,296,297,312,328,344,351,375,376,378,408,424,440,456,459,472,488, %U A375076 513,520,536,552,568,584,594,616,621,632,664,680,686,696,702,712,728,744,750 %N A375076 Numbers whose prime factorization exponents include at least one 1, at least one 3 and no other exponents. %C A375076 First differs from its subsequence A360793 at n = 79: a(79) = 1080 = 2^3 * 3^3 * 5 is not a term of A360793. %C A375076 Numbers k such that the set of distinct prime factorization exponents of k (row k of A136568) is {1, 3}. %C A375076 The asymptotic density of this sequence is ((zeta(6)/zeta(3)) * Product_{p prime} (1 + 2/p^3 - 1/p^4 + 1/p^5) - 1)/zeta(2) = 0.076359822332835689478... . %H A375076 Amiram Eldar, <a href="/A375076/b375076.txt">Table of n, a(n) for n = 1..10000</a> %H A375076 <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a>. %t A375076 Select[Range[750], Union[FactorInteger[#][[;; , 2]]] == {1, 3} &] %o A375076 (PARI) is(k) = Set(factor(k)[,2]) == [1, 3]; %Y A375076 Equals A336591 \ (A005117 UNION A062838). %Y A375076 Subsequences: A065036, A360793. %Y A375076 Cf. A002117, A013661, A013664, A136568. %K A375076 nonn,easy %O A375076 1,1 %A A375076 _Amiram Eldar_, Jul 29 2024