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#1
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![]() ͹ءÃÁẺ¹Õé ¨ÐÁÕÇÔ¸Õ¤Ô´ãËéäÇæÂѧ䧤ÃѺ |
#2
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![]() ÍéÒ§ÍÔ§:
$a_n=n^3-n^2$ $a_n=n(n+1)(n+2)-n(n+1)$ |
#3
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![]() ÍéÒ§ÍÔ§:
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