15 lines
559 B
Text
15 lines
559 B
Text
factor=: 3 : 0 NB. explicit
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'primes powers'=. __&q: y
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input_to_cartesian_product=. primes ^&.> i.&.> >: powers
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cartesian_product=. , { input_to_cartesian_product
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, */&> cartesian_product
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)
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factor=: [: , [: */&> [: { [: (^&.> i.&.>@>:)/ __&q: NB. tacit
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proper_divisors=: [: }: factor
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sum_of_proper_divisors=: +/@proper_divisors
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candidates=: 5 , [: +: [: #\@i. >.@-: NB. within considered range, all but one candidate are even.
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spds=:([:sum_of_proper_divisors"0(#\@i.-.i.&.:(p:inv))@*:)f. NB. remove primes which contribute 1
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