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A179202
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Numbers n such that phi(n) = phi(n+8), with Euler's totient function phi=A000010.
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7
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13, 16, 19, 25, 28, 32, 40, 70, 104, 128, 175, 182, 209, 280, 296, 488, 551, 584, 657, 715, 806, 910, 1232, 1256, 1544, 1602, 2022, 2048, 2216, 2288, 2504, 2540, 2590, 2717, 2912, 3176, 3368, 3640, 3656, 4060, 4328, 4904, 5246, 5288, 5320, 5384, 5864, 5969
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OFFSET
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1,1
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COMMENTS
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Among the 5596 terms below 10^7, a(6)=32 is the only term such that a(n+1) = a(n)+8.
There are 141741552 terms under 10^12. - Jud McCranie, Feb 13 2012
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LINKS
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FORMULA
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MATHEMATICA
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Select[Range[6000], EulerPhi[#] == EulerPhi[# + 8] &] (* Vincenzo Librandi, Sep 08 2016 *)
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PROG
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(PARI) {op=vector(N=8); for( n=1, 1e4, if( op[n%N+1]+0==op[n%N+1]=eulerphi(n), print1(n-N, ", ")))}
(Magma) [n: n in [1..10000] | EulerPhi(n) eq EulerPhi(n+8)]; // Vincenzo Librandi, Sep 08 2016
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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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