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A249397
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Composite numbers whose Euler totient divides the sum of the Euler totients of the numbers less than or equal to n and not relatively prime to n.
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3
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161, 171, 895, 1337, 1843, 1967, 2575, 5833, 8255, 36121, 54439, 87353, 195921, 274115, 284419, 340363, 368449, 387087, 444639, 504539
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OFFSET
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1,1
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COMMENTS
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No more terms < 10^6.
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LINKS
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EXAMPLE
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Numbers not coprime to 161 are 7, 14, 21, 23, 28, 35, 42, 46, 49, 56, 63, 69, 70, 77, 84, 91, 92, 98, 105, 112, 115, 119, 126, 133, 138, 140, 147, 154, 161 and the sum of their Euler totients is 1320; phi(161) = 132 and 1320/132 = 10.
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MAPLE
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with(numtheory): P:=proc(q) local a, k, n; for n from 1 to q do
if not isprime(n) then a:=0;
for k from 1 to n do if gcd(k, n)>1 then a:=a+phi(k); fi; od;
if type(a/phi(n), integer) then print(n); fi; fi; od; end: P(10^9);
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PROG
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(PARI) isok(n) = (n!=1) && !isprime(n) && (sum(k=1, n-1, if (gcd(k, n) != 1, eulerphi(k), 0)) % eulerphi(n) == 0); \\ Michel Marcus, Oct 29 2014
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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