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 A054039 #12 Oct 27 2023 22:00:46
%S A054039 0,4,13,32,113,322,1017,3206,10124,32043
%N A054039 a(n)^2 is the least square to contain n different decimal digits.
%C A054039 It turns out that "...at least n..." and "...exactly n..." yield the same (and thus strictly increasing) sequence. - _M. F. Hasler_, Feb 02 2009
%e A054039 13^2=169 is the first square to contain exactly 3 different digits; 322^2=103684 is the first square to contain exactly 6 different digits.
%o A054039 (PARI) A054039(n,k=0) = { while( #Set(Vec(Str(k^2)))<n, k++); k } /* If "exactly n" would correspond to a different sequence, this would yield some term twice in a row. The optional 2nd arg can be used to find further terms with a given # of distinct digits. - _M. F. Hasler_, Feb 02 2009 */
%Y A054039 Cf. A016069, A054031, A054032, A054033, A054034, A054035, A054036, A054037, A054038.
%K A054039 nonn,fini,full,base,easy
%O A054039 1,2
%A A054039 _Asher Auel_, Feb 28 2000
%E A054039 Minor rewording, added comment, keywords "easy,full" and PARI code _M. F. Hasler_, Feb 02 2009