It is: -3+8n-5 = 8n-8 when simplified
3 plus 3 plus 3 is 9. 3 plus 3 plus 3 plus 3 plus 3 plus 3 is 18.
The answer to your question is twenty four.
15
25
19 is the answer to 3 plus 4 plus 4 plus 3 plus 5
One possible answer, based on polynomial functions is Un = (8n5 - 140n4 + 920n3 - 2800n2 + 3887n - 1860)/15 for n = 1, 2, 3, ...
27x3+6=87.
3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 plus 3 is 54.
3 plus 3 plus 3 is 9. 3 plus 3 plus 3 plus 3 plus 3 plus 3 is 18.
The answer to your question is twenty four.
15
As stated, the sequence is best described as that generated by Un = (-8n5 + 135n4 - 812n3 + 2292n2 - 3047n + 1560)/6 for n = 1, 2, 3, ... There would have been a much simpler solution IF the third number had been 30, but it is not so the above is your answer.
25
19 is the answer to 3 plus 4 plus 4 plus 3 plus 5
It is 77
356,433,300
12