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A207080
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The smallest Carmichael number k such that phi(k) does not divide (k-1)^n, where phi is the Euler totient function.
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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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Conjecture: phi(a(n)) divides (a(n)-1)^(n+1).
a(10) <= 9645020063586019926451. - Daniel Suteu, Dec 25 2020
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LINKS
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PROG
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(PARI) is_c(n) = { my(f); bittest(n, 0) && !for(i=1, #f=factor(n)~, (f[2, i]==1 && n%(f[1, i]-1)==1)||return) && #f>1; }
isok(k, n) = ((k-1)^n % eulerphi(k)) != 0;
a(n) = my(k=1); while (!(is_c(k) && isok(k, n)), k++); k; \\ Michel Marcus, Dec 25 2020
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CROSSREFS
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KEYWORD
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nonn,more,changed
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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