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#2
23 àÁÉÒ¹ 2019, 22:32
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ÍéÒ§ÍÔ§:
$a_n=n^3-n^2$ $a_n=n(n+1)(n+2)-n(n+1)$ 
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#3
25 àÁÉÒ¹ 2019, 06:45
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ÍéÒ§ÍÔ§:
 
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