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 A381315 #7 Feb 21 2025 08:16:49
%S A381315 8,24,27,40,54,56,72,88,104,108,120,125,135,136,152,168,184,189,200,
%T A381315 232,248,250,264,270,280,296,297,312,328,343,344,351,360,375,376,378,
%U A381315 392,408,424,440,456,459,472,488,500,504,513,520,536,540,552,568,584,594
%N A381315 Numbers whose prime factorization exponents include exactly one 3 and no exponent greater than 3.
%C A381315 Subsequence of A176297 and A375072, and first differs from them at n = 20: A176297(20) = A375072(20) = 216 = 2^3 * 3^3 is not a term of this sequence.
%C A381315 The asymptotic density of this sequence is (1/zeta(3)) * Sum_{p prime} 1/(p+p^2+p^3) = 0.089602607198058453295... .
%H A381315 Amiram Eldar, <a href="/A381315/b381315.txt">Table of n, a(n) for n = 1..10000</a>
%t A381315 q[n_] := Module[{e = FactorInteger[n][[;; , 2]]}, MemberQ[e, 3] && Count[e, _?(# < 3 &)] == Length[e] - 1]; Select[Range[600], q]
%o A381315 (PARI) isok(k) = {my(e = factor(k)[, 2]~); select(x -> x > 2, e) == [3];}
%Y A381315 Subsequence of A046100, A176297, A375072 and A375145.
%Y A381315 Subsequences: A030078, A048109, A065036, A143610, A163569, A179670, A179695, A179700, A189975, A189984, A190109, A190378, A190382.
%Y A381315 Cf. A002117.
%K A381315 nonn,easy
%O A381315 1,1
%A A381315 _Amiram Eldar_, Feb 19 2025