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 A373589 #14 Dec 16 2024 13:18:07
%S A373589 1,8,20,44,50,64,68,92,110,116,125,160,164,170,188,212,230,236,242,
%T A373589 275,284,290,332,352,356,374,400,404,410,425,428,452,470,506,512,524,
%U A373589 530,544,548,575,578,590,596,605,638,668,692,710,716,725,736,764,782,788,830,880,890,902,908,928,932,935,956,986,1000
%N A373589 Numbers whose number of prime factors (with multiplicity) is a multiple of 3, and all of them are of the type 3m-1 (in A003627).
%C A373589 A multiplicative semigroup: if m and n are in the sequence, then so is m*n.
%H A373589 Antti Karttunen, <a href="/A373589/b373589.txt">Table of n, a(n) for n = 1..20000</a>
%e A373589 1 is a term since it has no prime factors, 0 is a multiple of 3, and "the empty set has every property". - _N. J. A. Sloane_, Dec 16 2024
%t A373589 Join[{1},Select[Range[1000],Mod[PrimeOmega[#],3]==0&&Union[Mod[FactorInteger[#][[;;,1]],3]]=={2}&]] (* _Harvey P. Dale_, Dec 16 2024 *)
%o A373589 (PARI) isA373589 = A373588;
%Y A373589 Cf. A001222, A003627, A121307 (subsequence), A373588 (characteristic function).
%Y A373589 Intersection of A004612 and A145784.
%Y A373589 Subsequence of A373597, which in turn is a subsequence of many other sequences.
%Y A373589 Cf. also A373590.
%K A373589 nonn,easy
%O A373589 1,2
%A A373589 _Antti Karttunen_, Jun 10 2024