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 A322571 #49 Sep 08 2022 08:46:23
%S A322571 4,15,32,55,84,119,455,799,900,3332,3535,7007,8855,244244,333332,
%T A322571 335335,400404,445444,555559,666464,799799,1999199,3303300,33333332,
%U A322571 33353335,3333333332,3333533335,333333333332,333335333335,700007077007,33333333333332,33333353333335,3333333333333332,3333333533333335
%N A322571 Positive integers A270710(k) (= (k+1)*(3*k-1)) which have only 1 or 2 different digits in base 10.
%H A322571 Giovanni Resta, <a href="/A322571/b322571.txt">Table of n, a(n) for n = 1..50</a>
%F A322571 a(n) = A270710(A322570(n)).
%F A322571 For k > 0, A002277(2*k) - 1 is a term.
%t A322571 Select[Table[(n+1)(3n-1),{n,3334*10^4}],Count[DigitCount[#],0]>7&] (* _Harvey P. Dale_, Jun 12 2022 *)
%o A322571 (PARI) for(k=1, 1e8, if(#Set(digits(j=3*k^2+2*k-1))<=2, print1(j", ")))
%o A322571 (Magma) [a:k in [1..10000000]| #Set(Intseq(a)) le 2 where a is (k+1)*(3*k-1)]; // _Marius A. Burtea_, Aug 29 2019
%Y A322571 Cf. A002277, A018885 (in case of squares), A213516 (in case of triangular numbers), A270710, A322570, A323639.
%K A322571 nonn,base
%O A322571 1,1
%A A322571 _Seiichi Manyama_, Aug 29 2019