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A272716
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Numbers equal to the sum of their proper divisors d such that d mod 3 = 1.
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2
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OFFSET
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1,1
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COMMENTS
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10^11 < a(4) <= 8581256320000.
The numbers equal to the sum of their proper divisors which are a multiple of 3 are the perfect numbers (A000396) multiplied by 3.
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LINKS
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EXAMPLE
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The proper divisors of 440 which are congruent to 1 mod 3 are 1, 4, 10, 22, 40, 55, 88, and 220. Since their sum is 440, 440 is a term.
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MATHEMATICA
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Select[Range[5000], # == Plus @@ Select[Most@ Divisors@#, Mod[#, 3] == 1 &] &]
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PROG
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CROSSREFS
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KEYWORD
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nonn,bref,more,hard
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AUTHOR
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STATUS
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approved
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