0 formulas included in custom cheat sheet 
Number of terms in the series: $n$
First term: $a_1$
$N^{th}$ term: $a_n$
Sum of the first $n$ terms: $S_n$
Difference between successive terms: $d$
Common ratio: $q$
Sum to infinity: $S$

$$ a_n = a_1 + (n1)d $$ 

$$ a_i = \frac{a_{i1} + a_{i+1}}{2} $$ 

$$ S_n = \frac{a_1 + a_n}{2} \cdot n $$ 

$$ S_n = \frac{2 \cdot a_1 + (n1) \cdot d}{2} \cdot n $$ 

$$ a_n = a_1 \cdot q^{n1} $$ 

$$ a_i = \sqrt{a_{i1} \cdot a_{i+1}} $$ 

$$ S_n = \frac{a_nq  a_1}{q1} $$ 

$$ S_n = \frac{a_1 \cdot \left(q^n  1 \right)}{q1} $$ 

$$ S = \frac{a_1}{1q}, \quad (\text{for } 1 < q < 1)$$ 
Please tell me how can I make this better.