Question

1,3,6,10,15

whats the 15th and 30th term

Answer 1

looks like the set of triangular numbers

\[a_{n} = a_{n -1} + n\]

Answer 2

@campbell_st what? im so confused..

Answer 3

the sequence is well know.... like the set of square numbers...

you can draw a triangle with numbers



the sequence is increasing by the counting numbers1, 1 + 2 = 3, 3 + 3 = 6, 6 + 4 = 10...

so the 6th number is 15 + 6 = 21 7th = 21 + 7 = 28

so the formula for a term is

\[a_{n} = \frac{n(n + 1)}{2}\]

check to see if the formula fits... if it does then its easy to find the 15th and 30th numbers in the sequence