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 A127174 #7 Feb 03 2019 12:26:35 %S A127174 3,9,21,24,30,33,39,48,51,57,63,75,102,111,129,138,147,162,180,189, %T A127174 195,198,207,222,225,231,240,249,267,270,288,297,330,336,339,342,348, %U A127174 351,354,357,363,369,372,381,396,399,402,405,411,429,432,465,468,477,480 %N A127174 Numbers n of the form 3*k such that partition number of n is also of the form 3*k. %C A127174 Subset of A083214. Or, intersection of A083214 and A008585. %p A127174 with(combinat): a:=proc(k): if numbpart(3*k) mod 3 = 0 then 3*k else fi end: seq(a(n),n=1..200); # _Emeric Deutsch_, Apr 16 2007 %t A127174 Select[Range[3,600,3],Mod[PartitionsP[ # ],3]==0&] %Y A127174 Cf. A000041, A008585, A083214, A087183. %K A127174 nonn %O A127174 1,1 %A A127174 _Zak Seidov_, Apr 05 2007