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a(n)^3 is smallest cube containing exactly n 9's.
21

%I #16 Oct 10 2019 23:24:05

%S 9,31,99,998,999,7937,9999,99998,99999,996999,999999,6688699,9999999,

%T 97609999,99969999,999999998,999899999,9998999999,9999999999,

%U 9999699999,99999989999,99998999999,997999998999

%N a(n)^3 is smallest cube containing exactly n 9's.

%C a(24) > 5*10^12, a(25) = 999996999999. - _Giovanni Resta_, Jun 29 2018

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/CubicNumber.html">Cubic Number</a>

%t (* A048374 *)

%t nsmall = Table[Infinity, 11];

%t For[i = 0, i <= 10^6, i++, n0 = Count[IntegerDigits[i^3], 9];

%t If[nsmall[[n0]] > i, nsmall[[ n0]] = i]];

%t nsmall(* _Robert Price_, Sep 26 2018 *)

%Y Cf. A036536, A048365, A048366, A048367, A048368, A048369, A048370, A048371, A048372, A048373.

%K nonn,base,more

%O 1,1

%A _Patrick De Geest_, Mar 15 1999

%E a(16)-a(22) from _Lars Blomberg_, Jun 12 2011

%E a(23) from _Giovanni Resta_, Jun 29 2018