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 A081328 #8 Oct 17 2021 04:21:00
%S A081328 0,1,2,3,4,4,6,6,8,9,9,9,12,12,12,12,16,16,18,18,18,18,0,18,24,24,24,
%T A081328 27,27,27,27,24,32,32,32,32,36,36,36,36,32,36,27,36,36,0,0,36,48,48,
%U A081328 48,48,0,48,54,54,54,54,32,54,0,54,54,48,64,64,64,64,0,64,0,64,72,72,72,72,0
%N A081328 Greatest 3-smooth number m such that n-m is also 3-smooth, a(n)=0 if no such 3-smooth number exists.
%F A081328 a(n)=0 iff A081326(n)=0; if a(n)>0: a(n)+A081327(n)=n.
%e A081328 a(32) = 24 = 3*2^3, as 32 = 2^3 + 24.
%t A081328 smooth3Q[n_] := n == 2^IntegerExponent[n, 2]*3^IntegerExponent[n, 3];
%t A081328 a[n_] := Module[{m}, For[m = n, m >= 1, m--, If[smooth3Q[m], If[smooth3Q[n - m], Return[m]]]]; 0];
%t A081328 Array[a, 77] (* _Jean-François Alcover_, Oct 17 2021 *)
%Y A081328 Cf. A081329, A081330, A081327, A000040, A003586.
%K A081328 nonn
%O A081328 1,3
%A A081328 _Reinhard Zumkeller_, Mar 19 2003