4, 12, 36, 108, ... - 

multiply previous term by 3 to get the next term

4, 12, 20, 28, .... - 

add 8 to the previous term to get the next term

4, 12, 22, 34, ... - 

add 8, then add 10, increasing the difference by 2 each time

4, 12, 21, 31, ... - 

add 8, then add 9, increasing the difference by 1 each time

4, 12, 28, 60, ... - 

multiply the previous term by 2 and add 4 to get the next term

24 - 

$$4^{th}$$ square number + $$2^{nd}$$ cube number

122 - 

$$1^{st}$$ triangular number + $$11^{th}$$ square number

100 - 

$$9^{th}$$ triangular number + $$10^{th}$$ triangular number

140 - 

$$5^{th}$$ cube number + $$5^{th}$$ triangular number

8 - 

$$6^{th}$$ square number − $$7^{th}$$ triangular number

0 - 

$$8^{th}$$ square number − $$4^{th}$$ cube number