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<DIV><FONT face=Arial size=2>For positive integers a, b, define sequence f as
follows</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>f(1) = a</FONT></DIV>
<DIV><FONT face=Arial size=2>f(2) = b</FONT></DIV>
<DIV><FONT face=Arial size=2>f(n+1) = PROD(1<=k<=n; f(k)) mod
SUM(1<=k<=n; f(k)).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Must f(n) = 0 for some
n?</FONT></DIV></BODY></HTML>