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A256907
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Numbers n such that phi(n) = 3*phi(n+1).
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4
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119, 527, 545, 2849, 3689, 4487, 6649, 18619, 26771, 30377, 44659, 47585, 50507, 76997, 83021, 102167, 112463, 128933, 138773, 163877, 174437, 192881, 193115, 198263, 217967, 236441, 243827, 244001, 254539, 268067, 282359, 287825, 298115, 345059, 410123, 464645
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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(545) = 3*phi(546) = 432.
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MATHEMATICA
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Select[Range@ 1000000, EulerPhi@# == 3 EulerPhi[# + 1] &] (* Michael De Vlieger, Apr 12 2015 *)
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PROG
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(PARI) s=[]; for(n=1, 1000000, if(eulerphi(n)==3*eulerphi(n+1), s=concat(s, n))); s \\ Colin Barker, Apr 12 2015
(Magma) [n: n in [1..2*10^6] | EulerPhi(n) eq 3*EulerPhi(n+1)]; // Vincenzo Librandi, Apr 13 2015
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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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