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 A224484 #21 Mar 06 2022 14:47:17
%S A224484 9,54,72,126,189,243,351,432,468,513,576,756,855,945,1008,1125,1332,
%T A224484 1395,1458,1512,1674,1755,1944,2205,2322,2331,2457,2709,2745,2808,
%U A224484 3087,3402,3456,3528,3591,3744,4104,4221,4608,4914,4941
%N A224484 Numbers which are the sum of two positive cubes and divisible by 3.
%C A224484 If 12*h-27 is a square then some values of 3*h are in this sequence. It is easy to verify that h is of the form 3*m^2-3*m+3, and therefore 9*(m^2-m+1) = (2-m)^3+(m+1)^3.
%C A224484 All entries are multiples of 9. [Proof: the cubes mod 3 are A010872. So the two cubes are either of the form (3i)^3 and (3j)^3 or (3i+1)^3 and (3j+2)^3. The same 3-periodic pattern is seen in the cubes modulo 9, A167176.] - _R. J. Mathar_, Aug 24 2016
%H A224484 Vincenzo Librandi, <a href="/A224484/b224484.txt">Table of n, a(n) for n = 1..1000</a>
%t A224484 upto[n_] := Block[{t}, Union@ Reap[ Do[If[Mod[t = x^3 + y^3, 3] == 0, Sow@ t], {x, n^(1/3)}, {y, Min[x, (n - x^3)^(1/3)]}] ][[2, 1]]]; upto[5000] (* _Giovanni Resta_, Jun 12 2020 *)
%t A224484 Module[{nn=20},Select[Union[Total/@Tuples[Range[nn]^3,2]],Mod[#,3]==0 && #<nn^3&]] (* _Harvey P. Dale_, Mar 06 2022 *)
%Y A224484 Cf. A224485 (divisible by k=5), A101421 (k=7), A101852 (k=11), A094447 (k=13), A099178 (k=17), A102619 (k=19), A101806 (k=23), A224483 (k=29), A102658 (k=31), A102618 (k=37).
%K A224484 nonn,easy
%O A224484 1,1
%A A224484 _Vincenzo Librandi_, May 10 2013