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PROJECT EULER · #0254

Sums of Digit Factorials

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Define f(n) as the sum of the factorials of the digits of n. For example, f(342)=3!+4!+2!=32.

Define sf(n) as the sum of the digits of f(n). So sf(342)=3+2=5.

Define g(i) to be the smallest positive integer n such that sf(n)=i. Though sf(342) is 5, sf(25) is also 5, and it can be verified that g(5) is 25.

Define sg(i) as the sum of the digits of g(i). So sg(5)=2+5=7.

Further, it can be verified that g(20) is 267 and sg(i) for 1i20 is 156.

What is sg(i) for 1i150?

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