%I #11 Mar 15 2024 17:56:20

%S 5,150,105,10052,10005,1000050,1000055,100000056,100000035,

%T 10000000050,10000000065,1000000000056,1000000000025,100000000000054,

%U 100000000000005,10000000000000256,10000000000000135,1000000000000000152,1000000000000000075,1000000000000000000500

%N Least multiple of n in which the n-th digit from left is 5.

%H Robert Israel, <a href="/A113560/b113560.txt">Table of n, a(n) for n = 1..995</a>

%e a(4) = 4 * 2513 = 10052, in which the fourth digit is 5.

%p f:= proc(n) local d,m,R,v;

%p for d from n do

%p R:= {};

%p for m from ceil(10^(d-1)/n) do

%p v:= m*n;

%p if v > 10^d then break fi;

%p v:= v mod 10^(d-n+1);

%p if member(v,R) then break fi;

%p if floor(v/10^(d-n)) = 5 then return m*n fi;

%p R:= R union {v};

%p od

%p od;

%p end proc:

%p map(f, [$1..30]); # _Robert Israel_, Mar 15 2024

%Y Cf. A113556, A113557, A113558, A113559.

%K base,easy,nonn

%O 1,1

%A _Amarnath Murthy_, Nov 06 2005

%E More terms from _Joshua Zucker_, May 03 2006