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A353977
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Sum of the nontrivial divisors of n whose arithmetic derivative divides n.
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0
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0, 2, 3, 6, 5, 5, 7, 6, 3, 7, 11, 9, 13, 9, 8, 6, 17, 14, 19, 11, 10, 13, 23, 17, 5, 15, 30, 13, 29, 16, 31, 22, 14, 19, 12, 18, 37, 21, 16, 11, 41, 12, 43, 17, 8, 25, 47, 29, 7, 32, 20, 19, 53, 41, 16, 13, 22, 31, 59, 20, 61, 33, 10, 22, 18, 16, 67, 23, 26, 24, 71, 26, 73
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = Sum_{d|n, d'|n, d>1} d, where d' is the arithmetic derivative of d.
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EXAMPLE
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The sum of the nontrivial divisors of 6 whose arithmetic derivative divides 6 is 2 + 3 = 5.
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MATHEMATICA
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d[1] = 0; d[n_] := n*Plus @@ ((Last[#]/First[#]) & /@ FactorInteger[n]); a[n_] := DivisorSum[n, # &, # > 1 && Divisible[n, d[#]] &]; Array[a, 100] (* Amiram Eldar, May 13 2022 *)
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PROG
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(PARI) ad(n) = vecsum([n/f[1]*f[2]|f<-factor(n+!n)~]); \\ A003415
a(n) = sumdiv(n, d, if ((d>1) && !(n % ad(d)), d)); \\ Michel Marcus, May 13 2022
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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