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PROJECT EULER · #0618

Numbers with a Given Prime Factor Sum

Statement only · SolvedOriginal problem ↗

Consider the numbers 15, 16 and 18:
15=3×5 and 3+5=8.
16=2×2×2×2 and 2+2+2+2=8.
18=2×3×3 and 2+3+3=8.
15, 16 and 18 are the only numbers that have 8 as sum of the prime factors (counted with multiplicity).

We define S(k) to be the sum of all numbers n where the sum of the prime factors (with multiplicity) of n is k.
Hence S(8)=15+16+18=49.
Other examples: S(1)=0, S(2)=2, S(3)=3, S(5)=5+6=11.

The Fibonacci sequence is F1=1, F2=1, F3=2, F4=3, F5=5, ....
Find the last nine digits of k=224S(Fk).

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