[math problem] [find law] [write formula] The first number is 6, the second number is 7, the third number is 9, the fourth number is 12, the fifth number is 16, the sixth number is 21, the seventh number is 27 What is the nth number? (formula)

an=1+2+3+…… +（n-1）+a1=n（n-1）/2+6
I hope it can help you,

Math problem (find rules): 0.1.3.8.21. (). (). () Fill in the following three numbers according to the rule

0.1.3.8.21. (55). (144). (377) 1 * 3 = 0 + 3 3 * 3 = 1 + 8 8 * 3 = 3 + 21 21 * 3-8 = 55 55 * 3-21 = 144 144 144 * 3-55 = 377 or 0.1.3.8.21. (56). (151). (410) 2 * (0 + 1) - (- 1) = 3 2 * (1 + 3) - 0 = 8 2 * (3 + 8) - 1 = 21 2 * (8 + 21) - 2 = 56 2 * (21 + 56) - 3 = 151 2 * (56 + 1

Find the rule 0 1 3 8 21 () 144

Fifty-five
1×3-0=3
3×3-1=8
8×3-3=21
21×3-8=55
55×3-21=144

1,3,8,21,55, --,

1,3,8,21,55,144
3*3-1=8
8*3-3=21
21*3-8=55
55*3-21=144

Find the law: 3,10,6,11,9,12, ()

Twelve

Find the rule 3,6,11,18,27, (), (), (), ()

Find the rule 3,6,11,18,27, (38), (51), (66), (83)
6=3+3
11=6+5
18=11+7
27=18+9
38=27+11
51=38+13
66=51+15
83=66+17
Wish you a happy study!

Find the rule 2,2,6,11,18?

Should it be wrong? It should be 2,3,6,11,18, right?
Add 1, 3, 5, 7, 9 to the preceding numbers
It should be 27, 38, 51

(1,6) (2,3) (3,2) (1,6)(2,3)(3,2)(4,_ )(5,_ )

The multiplication of two numbers is 6, so: (4,3 / 2), (5,6 / 5)

1,3,6,18,21,63, (), () 201603

Multiply by three and then add three. You see, 1x3 = 3 3 + 3 = 6, 3x6 = 18

Number finding rule 1,2,4,3,5,6,9,18, () Please explain in detail

The odd number terms are found as follows: 1.4.5.9. It is found that the sum of the first two terms is equal to the last number, i.e. 1 + 4 = 5 4 + 5 = 9 5 + 9 = 14
The product of the first two terms is equal to the latter one, that is, 2 * 3 = 63 * 6 = 18
And () is exactly an odd number, so the answer is 14. If you want to fill in the next number, it is an even number. It should be 6 * 18 = 108

[math problem] [find law] [write formula] The first number is 6, the second number is 7, the third number is 9, the fourth number is 12, the fifth number is 16, the sixth number is 21, the seventh number is 27 What is the nth number? (formula)