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Search: id:A105261
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| A105261 |
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Values of n such that phi(n)=c(n)^2, where phi is the Euler totient function and c(n) is the product of the distinct prime factors of n (c(1)=1). |
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1
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OFFSET
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1,2
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COMMENT
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This sequence has exactly six terms (see the Monthly reference). phi(n)=A000010(n); c(n)=A007947(n).
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REFERENCES
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J.-M. De Konick, Problem 10966, Amer. Math. Monthly, 111 (2004), p. 536.
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EXAMPLE
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8 is in the sequence because phi(8)=4 (1,3,5,7), c(8)=2 (2 being the only prime divisor of 8) and so phi(8)=c(8)^2.
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MAPLE
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with(numtheory): c:=proc(n) local div: div:=convert(factorset(n), list): product(div[j], j=1..nops(div)) end:p:=proc(n) if phi(n)=c(n)^2 then n else fi end: seq(p(n), n=1..42000);
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CROSSREFS
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Cf. A000010, A007947.
Sequence in context: A099695 A000845 A027013 this_sequence A099762 A119936 A048543
Adjacent sequences: A105258 A105259 A105260 this_sequence A105262 A105263 A105264
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KEYWORD
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fini,nonn,full
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AUTHOR
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Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 14 2005
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