A linear sequence has first term $108$ and second term $103$. Find its first negative term.

Find the general formula for the following sequence.

$4,7,12,19,28,39,\dots$

Find the general formula for the following sequence.

$-7,-4,1,8,17,28,\dots$

Find the general formula for the following sequence.

$3.5,6.5,11.5,18.5,27.5,38.5,\dots$

Find the general formula for the following sequence.

$2,6,12,20,30,42,\dots$

Find the general formula for the following sequence.

$-1,0,3,8,15,24,\dots$

Find the general formula for the following sequence.

$6,14,24,36,50,66,\dots$

Find the general formula for the following sequence.

$-0.5,1,4.5,10,17.5,27,\dots$

Find the general formula for the following sequence.

$1,2,5,10,17,26,\dots$