One simple argument

T_100=5050,is clearly divisible by 5+5=10
T_1000=500500,
...
T_10^{k+1}=50...050...0, with k zeros sandwiched between the two 5's and another k zeros trailing the second 5, which is clearly divisible by 10 for all k>=1.

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• 回複：One simple argument -cma- ♂ (18 bytes) () 10/21/2009 postreply 19:37:07

• like this one -亂彈- ♂ (0 bytes) () 10/21/2009 postreply 20:13:19