24
The series formula is A(n) = n2 - 1
12 - 1 = 0
22 - 1 = 3
32 - 1 = 8
42 - 1= 15
52 - 1 = 24
63
The sequence appears to be multiplying by increasing factors: (3 \times 5 = 15) and (15 \times 5 = 75). Following this pattern, the next number would be (75 \times 5 = 375). Therefore, the next number in the sequence is 375.
The next number in the sequence 3-15-6-30-21 is -207.
I'm guessing your sequence is 1, 3, 6, 10, 15, ... In which case it continues: 21, 28, 36, 45, 55, 66, ... (These are the triangular numbers.)
5
5
63
The sequence appears to be multiplying by increasing factors: (3 \times 5 = 15) and (15 \times 5 = 75). Following this pattern, the next number would be (75 \times 5 = 375). Therefore, the next number in the sequence is 375.
17?
15
The numbers are increasing by 1,4,9,16,25,36.... which are square numbers so the next increase is 49. Making the next number in the sequence 141
5+5 = 10 10+5 = 15 15-5 = 15 10+5 = 15
The next number in the sequence 3-15-6-30-21 is -207.
18
The next number could be 26 The next number could be 12 - - - - - - - - - The next number that is in the sequence is 12.
44. You're adding 11 then 9 each time !
.75