I am on thin ice both syntax-wise and English-wise here, apologise if my way of expressing maths here is a rambling of a mad-man.
I have two sequences/"functions" f(n) and g(n). They are technically not functions, I have them just defined as a sequence of repeating modulus of 9 and 10.
n = 0,1,2,3,...
f(n): nMOD9={0,3,4,6}
g(n): nMOD10={0,3,4,5,8,9}

This means that f(n) is will go 0,3,4,6,9,12,13,15,18,ect. Just repeating the four numbers in the brackets of modulus of 9. 

g(n) will be 0,3,4,5,8,9,10,13,14,15,18,19,20,ect. Repeating the six numbers in brackets of modulus of 10.

Now I wonder, can I express h(n) which is the list of numbers that is both present in f(n) and g(n)? This will be 0,3,4,9,13,15,18,ect. Either as a function or as some nMODx={a,b,c}? Or some other genius way I have not thought about. 

Currently I do a manual check of both list, and I wonder if can be done more elegant.

How to express h(n) which is the "union" of the two sequences f(n) & g(n)
One possible solution would be to find all values of h(n) up to 90, then h(n) will be those nMOD90, so
h(n): nMOD90={0,3,4,9,13,15,18,24,30,33,39,40,45,48,49,54,58,60,63,69,75,78,84,85}

