%I #4 Sep 29 2014 02:27:39
%S 1,6,18,12,105,24,36,48,495,60,400,192,144,120,4656,180,1600,240,576,
%T 1120,10000,360,1296,2240,900,960,28920,720,25600,840,9216,5600,5184,
%U 1260,102400,6160,36864,1680,302500,2880,19600,15360,3600,12320
%N Smallest number m such that A174903(m) = n.
%C A174903(a(n)) = n and A174903(m) <> n for m < a(n).
%e a(2)=18, A174903(18)=#{(2,3),(6,9)}=2;
%e a(3)=12, A174903(12)=#{(2,3),(3,4),(4,6)}=3;
%e a(4)=105, A174903(105)=#{(3,5),(5,7),(15,21),(21,35)}=4;
%e a(5)=24, A174903(24)=#{(2,3),(3,4),(4,6),(6,8),(8,12)}=5.
%o (Haskell)
%o import Data.List (elemIndex); import Data.Maybe (fromJust)
%o a174904 = (+ 1) . fromJust . (`elemIndex` map a174903 [1..])
%o -- _Reinhard Zumkeller_, Sep 29 2014
%K nonn
%O 0,2
%A _Reinhard Zumkeller_, Apr 01 2010