# Number Pyramids

A number pyramid is created such that the number in the pink triangle is equal to the sum of pairwise products of the 3 neighboring numbers in yellow triangles. For instance, in the left pyramid above, $$11 = 1\cdot 2 + 2\cdot 3 + 3\cdot 1$$.

The right pyramid has number $$4$$ on top and $$1,3,5,7,9$$ in the remaining 5 yellow triangles.

If each of $$a, b, c$$ in the pink triangles is a composite number, compute $$a+b+c$$.

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