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Find the rules: 1, 2, 4, 7, 11 Find the number I know what the 2nd floor said
1=1
2=1+1
4=2+2
7=4+3
11=7+4
16=11+5
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an=a(n-1)+(n-1)
Add the above formula
a1+a2+a3+----+a(n-1)+an=a1+[a1+a2+a3+----+a(n-1)]+(1+2+3+----+n-1)
an=1+[1+2+3+----+(n-1)]
=1+(1+n-1)(n-1)/2
=(n²-n+2)/2
The nth is (n & sup2; - N + 2) / 2
Find rules 1, 3, 4, 7, 11, (), ()
18、29
The latter is the sum of the first two
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Please ask the answer of a question: find the rule to fill in 1, 3, 4, 7, 11, 18, (), ()
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Find the rules 1,3,4,7,11, (), (), ()
1.3.4.7.11.18.29.47
4=1+3
7=3+4
11=4+7
18=7+11
29=11+18
47=18+29
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