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 A135122 #11 Aug 09 2018 03:27:27
%S A135122 1,21,261,273,17748,17749,20820,20821,65620,65621,70740,70741,83268,
%T A135122 83269,86292,86293,1066068,1066069,1070420,1135701,1135893,1135953,
%U A135122 5326161,5330001,5330241,5330260,5330261,5506389,5525829,5526801,5571909,5574933,5592321
%N A135122 Numbers such that the digital sum base 2 and the digital sum base 3 and the digital sum base 4 all are equal.
%H A135122 Giovanni Resta, <a href="/A135122/b135122.txt">Table of n, a(n) for n = 1..10000</a>
%e A135122 a(2)=21, since ds_2(21)=ds_3(21)=ds_10(21)=3, where ds_x=digital sum base x.
%t A135122 Select[Range[5600000],Length[Union[Table[Total[IntegerDigits[#,n]],{n,2,4}]]]==1&] (* _Harvey P. Dale_, Aug 14 2013 *)
%o A135122 (PARI) isok(n) = my(sd2=sumdigits(n, 2)); (sd2==sumdigits(n, 3)) && (sd2==sumdigits(n, 4)); \\ _Michel Marcus_, Aug 08 2018
%Y A135122 Cf. A007953, A054899, A131451, A133620, A133900, A134599, A135100, A135110, A135120, A037308.
%K A135122 nonn,base
%O A135122 1,2
%A A135122 _Hieronymus Fischer_, Dec 31 2007
%E A135122 a(31)-a(33) from _Giovanni Resta_, Aug 06 2018