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A229552
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Numbers k such that phi(k) = phi(k+2) - phi(k+1).
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2
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1, 3, 5, 9, 15, 21, 35, 39, 45, 99, 135, 231, 255, 855, 1035, 1295, 1539, 1599, 2015, 4335, 6525, 9177, 14399, 16095, 30495, 55385, 61131, 62799, 65535, 72579, 77615, 110175, 152649, 179295, 244965, 299649, 603459, 619695, 686735, 1876725, 2841915, 3058209
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OFFSET
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1,2
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LINKS
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FORMULA
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MATHEMATICA
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Select[Range[10^6], EulerPhi[#] == EulerPhi[# + 2] - EulerPhi[# + 1] &]
Position[Partition[EulerPhi[Range[31*10^5]], 3, 1], _?(#[[3]]-#[[2]] == #[[1]]&), 1, Heads->False]//Flatten (* Harvey P. Dale, Nov 29 2017 *)
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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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