Use 123 three digits to form four digits. Among the possible four digits, how many are at least two consecutive digits 2? Why 19? What are there?

It can be divided into three categories: 1. There are two consecutive 2:3 * 2 * 2; 2. There are three consecutive 2:3 * 2; 3. There are four two: 1

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1. Choose a number from the three numbers 123, two numbers and three numbers to form one digit, two digit and three digit respectively. Which of them are prime numbers? emergency
2. 1. Use 123 to form () different three digit numbers, The smallest one is (). 709 can be used to form () different two digit numbers, and the largest one is () 2. There are five different colors of coats and three different colors of trousers. If you want to match them, you can have () sets of different costumes at most
3. 1+2+3+4+123+1+2+3+4+123=
4. 123+4=?
5. 123+234+456+567+678+789 fifty-five thousand five hundred and fifty-five fast Simple calculation OK, there are points
6. When a is greater than B and greater than 0, find (root a-root b) divided by root a + root B And a + B = 6 times root (AB)
7. Mathematics 123 ha ha
8. Mathematical puzzle 123 If C is a positive integer, and a + B = C, B + C = D, D + a = B, then what is the minimum value of (a + b) (B + C) (c + D) (D + a)?
9. Mathematical calculation 123 As shown in the figure, M is a moving point on ad in the parallelogram ABCD to know that the area of the parallelogram ABCD is a, so does the area of the triangle MBC change? Why?
10. Root a ^ 2 = () (a > 0) ()(a=0) ()(a
11. How many quadruple digits can be made up of 123? Please list them one by one
12. How many three digit numbers can be composed of the numbers 1, 2, 3, 4 and 5 without repetition, and 2 and 3 are not adjacent?
13. Use the three numbers 123 to make up four digits. Among the four digits that may be made up, how many are there at least two consecutive digits that are 2?
14. 1=5 2=12 3=123 4=1234 5=?
15. 123+123+123+123-123-123+1.23
16. 123+123+123+123+123+123+123+123+123+123-123-123-123-123-123=?
17. In Python, replace all the multiples of 3 from 1 to 123 with a First use in Python def main(): for num in range (1,124): print(num) Numbers from 1 to 123 appear Then I want to replace all the multiples of 3 with "a", all the multiples of 5 with "B", and all the common multiples of 3 and 5 with "C". How can I do that? It's Python 3.3
18. From 1 to 9999, how many permutations are there in the combination of the three numbers 123? How many numbers with 123, 213 or 321 can appear in 9999? The position is unlimited, and the form can also be: 0123, 1123, 1233, 1234. Please give the calculation method? There are 123 disjoint permutations, such as 1023, 1203, 3120 or 9123, 1293, etc. How many permutations can there be in 9999?
19. How many three digits can be made up of 123? What is the sum of them
20. 123 is a very simple number. Q: what is the maximum number represented by these three numbers?