%I
%S 123,41,5,589,347,193,471,15,419,217,863,701,25,449,487,133,731,35,
%T 679,157,3,561,45,109,227,473,191,55,739,697,543,621,65,569,567,213,
%U 851,75,599,837,483,881,85,829,507,353,711,95,259,577,823,341,105,889,47,893
%N a(n) is k such that k*(2n+1) mod 1000 = 123, or 2n+1 if no such k exists.
%C Contains odd numbers from 1 to 999. See patterns in graph.
%H Zak Seidov, <a href="/A125097/b125097.txt">Table of n, a(n) for n = 0..499</a>
%e n=3: a(3)=589 because 2n+1=7, 7*589 = 4123 = 123 (mod 1000).
%e n=499: a(499)=877 because 2n+1=999 and 999*877=876123 = 123 (mod 1000).
%K nonn
%O 0,1
%A _Zak Seidov_, Nov 20 2006
