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 A145784 #27 May 16 2025 07:32:14
%S A145784 1,8,12,18,20,27,28,30,42,44,45,50,52,63,64,66,68,70,75,76,78,92,96,
%T A145784 98,99,102,105,110,114,116,117,124,125,130,138,144,147,148,153,154,
%U A145784 160,164,165,170,171,172,174,175,182,186,188,190,195,207,212,216,222
%N A145784 Numbers with property that their number of prime factors counted with multiplicity is a multiple of 3.
%C A145784 A multiplicative semigroup: if m and n are in the sequence, then so is m*n. - _Antti Karttunen_, Jul 02 2024
%H A145784 Reinhard Zumkeller, <a href="/A145784/b145784.txt">Table of n, a(n) for n = 1..10000</a>
%F A145784 A010872(A001222(a(n))) = 0.
%t A145784 Join[{1}, Select[Range[2,230], Mod[Total[Transpose[FactorInteger[#]][[2]]], 3] == 0 &]] (* _T. D. Noe_, May 21 2012 *)
%o A145784 (Haskell)
%o A145784 a145784 n = a145784_list !! (n-1)
%o A145784 a145784_list = filter ((== 0) . a010872 . a001222) [1..]
%o A145784 -- _Reinhard Zumkeller_, May 26 2012
%o A145784 (PARI) isok(k) = !(bigomega(k) % 3); \\ _Amiram Eldar_, May 16 2025
%Y A145784 Cf. A001222, A010872, A373975 (characteristic function).
%Y A145784 Subsequences: A000578, A014612, A046316, A121307, A373589, A373590, A373597, A373837.
%Y A145784 Cf. also A028260, A214195, A297845.
%K A145784 nonn
%O A145784 1,2
%A A145784 _Reinhard Zumkeller_, Oct 19 2008