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A070639 a(n) = (1/phi(n))*Sum_{k=1..n} phi(n*k). 1
1, 3, 5, 9, 11, 20, 19, 31, 33, 48, 43, 73, 59, 90, 88, 111, 97, 159, 121, 182, 165, 208, 173, 277, 211, 290, 263, 338, 271, 445, 309, 435, 396, 490, 414, 608, 433, 610, 544, 695, 531, 844, 585, 818, 745, 880, 697, 1080, 773, 1085, 918, 1126, 883, 1364, 995 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
a(2n)>a(2n+1) for n>=5.
If n is prime, a(n) = A002088(n)+1. - Robert Israel, Aug 10 2020
LINKS
MAPLE
f:= n -> add(numtheory:-phi(n*k), k=1..n)/numtheory:-phi(n);
map(f, [$1..100]); # Robert Israel, Aug 10 2020
MATHEMATICA
Table[1/EulerPhi[n]*Sum[EulerPhi[n*k], {k, n}], {n, 60}] (* Harvey P. Dale, Dec 21 2015 *)
PROG
(PARI) for(n=1, 100, print1(sum(i=1, n, eulerphi(n*i))/eulerphi(n), ", "))
CROSSREFS
Cf. A002088.
Sequence in context: A213208 A282098 A034760 * A078392 A364808 A187753
KEYWORD
easy,nonn,look
AUTHOR
Benoit Cloitre, May 13 2002
STATUS
approved

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Last modified March 29 08:01 EDT 2024. Contains 371265 sequences. (Running on oeis4.)