[中學] 遞迴

[justin0602 (justin)]

a_1=1

a_n+1 = 2 a_n + n

求a_n

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◆ From: 1.164.4.216
→ zxcv0011    :先換成(a_n+1 + n+2) = 2(a_n + n+1)
推 ALGO        :令an+1-k=2(an-k)展開與題目給的式子對照求k。再用
推 coolbetter33:[3*2^(n-1)]-n-1