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A072155 Denominator of Sum_{k=1..n} phi(k)/k. 4
1, 2, 6, 3, 15, 5, 35, 70, 210, 210, 2310, 770, 10010, 10010, 30030, 15015, 255255, 255255, 4849845, 4849845, 4849845, 4849845, 111546435, 37182145, 37182145, 37182145, 111546435, 111546435, 3234846615, 3234846615, 100280245065, 200560490130, 200560490130 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..33.

EXAMPLE

1, 3/2, 13/6, 8/3, 52/15, 19/5, 163/35, 361/70, 1223/210, ...

MATHEMATICA

Table[Sum[EulerPhi[k]/k, {k, n}], {n, 40}]//Denominator (* Harvey P. Dale, Jun 08 2017 *)

PROG

(PARI) a(n) = denominator(sum(k=1, n, eulerphi(k)/k)); \\ Michel Marcus, Jan 26 2015

CROSSREFS

Cf. A071708 (numerators), A250031, A250032, A250034.

Sequence in context: A055773 A111866 A251753 * A094299 A121566 A056839

Adjacent sequences:  A072152 A072153 A072154 * A072156 A072157 A072158

KEYWORD

nonn,frac

AUTHOR

N. J. A. Sloane, Jun 28 2002

STATUS

approved

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Last modified August 22 12:56 EDT 2017. Contains 290948 sequences.