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1, 2, 3, 7, 8, 9, 10, 14, 17, 18, 19, 23, 24, 25, 26, 42, 43, 46, 47, 51, 52, 53, 54, 58, 63, 64, 91, 95, 96, 97, 98, 114, 115, 116, 117, 129, 130, 131, 132, 136, 137, 138, 139, 143, 146, 147, 148, 164, 171, 176, 177, 181, 182, 209, 210, 214, 215, 216, 217
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Accumulate@ Table[GCD[n, If[Abs@ n < 2, 0, n Total[#2/#1 & @@@ FactorInteger@ Abs@ n]]], {n, 58}] (* Michael De Vlieger, Feb 14 2016 *)
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PROG
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(Ruby)
require 'prime'
def a003415(n)
return 0 if n == 1
return 1 if Prime.prime?(n)
a = Prime.each.find { |i| n % i == 0 }
a * a003415(n/a) + n/a * a003415(a)
end
def a268398(n)
sum = 0
(1..n).map { |n| sum += a003415(n).gcd(n) }.last
end
(PARI) a085731(n) = {my(f = factor(n)); for (i=1, #f~, if (f[i, 2] % f[i, 1], f[i, 2]--); ); factorback(f); }
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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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