Answer: 123454321
Step-by-step explanation:
The given sequence : [tex]1\ 121\ 12321\ 1234321[/tex]
We can note that this is a symmetric sequence i.e. the digits in the numbers of the sequence are symmetric .
In the first number there is 2 in the middle and 1 is symmetric.
In the second number there is 3 in the middle and 1 and 2 are symmetric.
Similarly In the third number there is 4 in the middle and 1,2 and 3 are symmetric.
Then in the next number there must be 5 in the middle and 1,2,3,4 must be symmetric.
Hence, the next number must be 123454321
