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Which number does not belong in the series below?

$2, 5, 10, 17, 26, 37, 50, 64$

1. $17$
2. $37$
3. $64$
4. $26$
edited | 784 views

If $\large a_1,a_2,a_3\ldots a{_n}$ is the series and $i = 1$ to $n,$ then the series is defined as $a_i=i{^2} + 1.$
i.e the $i^{th}$ term is $1$ plus the square of $i.$
Series will be as follows $:1^{2} +1 ,2^{2}+ 1,3^{2} +1,4^{2}+1\ldots n^{2} + 1$
$\qquad\qquad\qquad\qquad\quad\;\; 2,5,10,17,26,37,50,65$

Hence $64$ does not belong to the series.
answered by Active (3.7k points)
edited
0
I could not find the series pattern.. but I observed here every even number is followed by a odd number... so 50 should have been followed by a odd number but 64 is a even!!... so I chose option (C).. anyway your solution is perfect!!
+5
Add consecutive odd number to previous number

2 + 3 = 5
5 + 5 = 10
10 + 7 = 17
17 + 9 = 26
26 + 11 = 37
37 + 13 = 50
50 + 15 = 65
–1 vote

2,5,10,17,26,37,50,64
(even),(odd),(even),(odd),(even),(odd),(even),(even).
so 50 is at even position then 64 should be odd number but 64 is even ...so 64 will be not be here

answered by Active (4.2k points)

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