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A072157
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Denominator of Sum_{k=1..n} phi(k)/k^2.
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2
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1, 4, 36, 72, 1800, 1800, 88200, 176400, 529200, 105840, 12806640, 12806640, 2164322160, 2164322160, 10821610800, 21643221600, 6254891042400, 6254891042400, 2258015666306400, 451603133261280, 451603133261280, 451603133261280, 238898057495217120, 238898057495217120
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..300
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EXAMPLE
| 1, 5/4, 53/36, 115/72, 3163/1800, 3263/1800, 170687/88200, ...
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MATHEMATICA
| Denominator[Table[Sum[EulerPhi[k]/k^2, {k, n}], {n, 30}]] (* From Harvey P. Dale, Nov 13 2011 *)
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CROSSREFS
| Cf. A072156.
Sequence in context: A091722 A053939 A167632 * A075215 A193833 A193183
Adjacent sequences: A072154 A072155 A072156 * A072158 A072159 A072160
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KEYWORD
| nonn,frac
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jun 28 2002
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