How to express the general term formula of 2,222?

2/9(10^n-1)

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1. 2 + 22 + 222 + 2222 + ellipsis + 222
2. Please help me. Number 1.0.3.4.13.12.39 The general term formula of If possible, please write the derivation
3. Sum of sequence: 2 + 22 + 222 + +22… 222 (N 2) an=2/9(10^n-1) The answer is Sn = [20 * (10 ^ n-1)] / 81-2 / 9N I want to ask Sn how the answer comes out
4. s=2+22+222+2222+…… +2222…… How to calculate the sum of 2222 (N 2's),
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6. 2+2+2-2+22-222-2+2222
7. What is the law of calculating 2 * 22 * 22 222 * 222 2222 * 2222?
8. Find the rule first, then fill in the number 2 / 1 / 4 / 3 1 / 8 1 / 16 11 ()（ It has to be done now. It's better to have a process, hehe
9. (1) 1 / 16,1 / 8,3 / 16,1 / 4, (), () (2) 1,3,4,7,11, (), (), 47 （3）8,4,2,1,1/2,1/4,（）,（）
10. Find the rules (1) 1,1,1,3,3,5, (), 11 (2) 7,7,16,42107, () (3) 1,2,3,1,4,4,7, (), 6
11. General term formula of sequence 4,13,40121 4.13.40.121 . I know that each term is the first term * 3 + 1, but I want the general term formula not the recursive formula
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13. How to find the sequence 7,9,13,19 by guessing ideas (analysis method) The general term formula of Is there any formula or something like that An = an + BN and so on
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17. 3.5.9.17.33. General term formula of sequence
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