login
a(n)^2 is the least square to contain n different decimal digits.
13

%I #12 Oct 27 2023 22:00:46

%S 0,4,13,32,113,322,1017,3206,10124,32043

%N a(n)^2 is the least square to contain n different decimal digits.

%C 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 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 (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 Cf. A016069, A054031, A054032, A054033, A054034, A054035, A054036, A054037, A054038.

%K nonn,fini,full,base,easy

%O 1,2

%A _Asher Auel_, Feb 28 2000

%E Minor rewording, added comment, keywords "easy,full" and PARI code _M. F. Hasler_, Feb 02 2009