Find out the wrong number.
2, 5, 10, 17, 26, 37, 51

To find the wrong number in the given sequence, let us analyze the pattern of the numbers:
2, 5, 10, 17, 26, 37, 51

Let us examine the difference between consecutive terms in the sequence:
First term: 2
Second term: 5 (difference: $5-2=3$)
Third term: 10 (difference: $10-5=5$)
Fourth term: 17 (difference: $17-10=7$)
Fifth term: 26 (difference: $26-17=9$)
Sixth term: 37 (difference: $37-26=11$)

We can observe that the differences between consecutive terms are successive odd numbers: 3, 5, 7, 9, 11.
Following this pattern, the difference between the sixth term and the seventh term should be the next odd number, which is 13.

Let us calculate what the seventh term should be:
$37+13=50$

Alternatively, we can express each term in the form of $n^2+1$ for $n=1,2,3,...$:
$1^2+1=1+1=2$
$2^2+1=4+1=5$
$3^2+1=9+1=10$
$4^2+1=16+1=17$
$5^2+1=25+1=26$
$6^2+1=36+1=37$
$7^2+1=49+1=50$

However, the given sequence has 51 instead of 50 as the last term. Therefore, 51 is the wrong number in the sequence.

The correct option is 51.