The sequence is a combination of two series :

I.  19, 38, 114, (….)        and     II.  2, 3, 4
The pattern followed in I is * 2, * 3,…
.’. Missing number = 114 * 4 = 456.

8 * 0.5 = 4
4 * 1 = 4
4 * 2 = 8
8 * 4 = 32
32 * 8 = 256

8 + 1² + 1= 10
10 + 3² + 1= 20
20 + 5² + 1= 46……..

8 * 0.5 = 4
4 * 1 = 4
4 * 1.5 = 6
6 * 2 = 12
12 * 2.5 = 30

18 * 1 + 2 = 20
20 * 2 – 4 = 36
36 * 3 + 6 = 114
114 * 4 – 8 = 448
448 * 5 + 10 = 2250

11 + 1² + 1= 13
13 + 2² + 1= 18
18 + 4² + 1= 35……..

1650/6 – 5 = 275 – 5 = 270
270/5 -4 = 54-4 = 50
50/4 -3 = 12.5 -3 = 9.5
9.5/3 -2 = 3.17-2 = 1.17
1.17/2 -1 = 0.585-1 = -0.415

520*1/5 =104
104*2/5= 41.6
41.6*3/5 = 24.96
24.96*4/5 = 19.97

11*1+(1*7) =11+7 = 18
18*2+(2*6) = 36+12 = 48
48*3+(3*5) = 144+15 = 159
159*4+(4*4) = 636+16 = 652