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A189057
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Numbers n for which phi(n)=sigma(n'), where phi is the Euler totient function, sigma is the sum of divisors and n' the arithmetic derivative of n.
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2
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2, 57, 175, 357, 381, 543, 777, 903, 2379, 3027, 6807, 25823, 47047, 74333, 82621, 136213, 153425, 163471, 194873, 230547, 257799, 259555, 265111, 269545, 285439, 289009, 302403, 305305, 311395, 354365, 416005, 484169, 569245, 718333, 755885, 781501, 1012505
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OFFSET
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1,1
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LINKS
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EXAMPLE
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phi(57)=36. 57'=22 and sigma(22)=36
phi(1012505)=725760. 1012505'=310156 and sigma(310156)=725760
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MAPLE
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with(numtheory);
P:=proc(i)
local f, n, p, pfs;
for n from 1 by 1 to i do
pfs:=ifactors(n)[2];
f:=n*add(op(2, p)/op(1, p), p=pfs);
if phi(n)=sigma(f) then print(n); fi;
od;
end:
P(1000000)
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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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