Urgent! Sequence 11991, 1990, 11989... From the third number, each number is the difference between the first two numbers, in which item does the first zero appear? There should be process and explanation, quick! OK, I'll add points!

1 11991 21990 3 1991-11 41989 5 1991-21988 6 1991-31 71987 8 1991-41986 9 1991-5. It can be seen that a (3n-2) = 1a (3n-1) = 1991-2 (n-1) a (3n) = 1991 - [2 (n-1) + 1] = 1992-2na (3n-1) its value is odd and cannot be 0

What is the 2011 item of Rabbit Series

If all rabbits do not die, how many pairs of rabbits can be bred in one year? We might as well take the new born one as an example. The obvious feature is that the sum of the two adjacent terms in the front constitutes the latter

Will the selection of the first number and the second number in the rabbit sequence affect my research findings? Why? My findings are in the supplementary question
My discovery: the sum of the first n numbers in the rabbit sequence = the (n + 2) - the second number

You write recursion like this
A0+A1=A2
A1+A2=A3
…………
An+An+1=An+2
Then add it all up and eliminate those terms, and your induction is proved
Very careful!

Urgent! Sequence 11991, 1990, 11989... From the third number, each number is the difference between the first two numbers, in which item does the first zero appear? There should be process and explanation, quick! OK, I'll add points!