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A073544
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Numbers n such that 1/(1/phi(n) + 1/phi(n+1) + 1/phi(n+2) + 1/phi(n+3)) is an integer.
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0
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13, 75, 111, 144, 192, 558, 559, 1683, 2016, 3624, 7129, 10369, 11658, 18362, 19442, 19800, 19801, 32772, 47627, 60482, 82082, 133988, 143642, 229321, 291721, 312483, 352846, 390603, 395136, 436801, 465482, 600601, 711936, 806736, 819729
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| 1/phi(75)+1/phi(76)+1/phi(77)+1/phi(78) = 1/40+1/36+1/60+1/24 = 1/9 so 75 is in the sequence.
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MATHEMATICA
| Select[Range[900000], IntegerQ[1/Sum[1/EulerPhi[ #+i], {i, 0, 3}]]&]
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CROSSREFS
| Sequence in context: A139070 A094421 A103968 * A051361 A114070 A005340
Adjacent sequences: A073541 A073542 A073543 * A073545 A073546 A073547
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 27 2002
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EXTENSIONS
| Edited by Dean Hickerson (dean.hickerson(AT)yahoo.com), Sep 03 2002
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