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A332686 a(n) = Sum_{k=1..n} phi(k/gcd(n, k)). 2
1, 2, 3, 5, 7, 9, 13, 18, 21, 23, 33, 33, 47, 49, 51, 67, 81, 76, 103, 97, 103, 119, 151, 135, 163, 173, 185, 189, 243, 185, 279, 280, 265, 299, 291, 291, 397, 379, 369, 371, 491, 381, 543, 491, 455, 553, 651, 539, 653, 610, 643, 683, 831, 689, 743, 753, 801, 887, 1029 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Inverse Moebius transform of A053570.

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = Sum_{k=1..n} phi(lcm(n, k)/n).

a(n) = Sum_{d|n} A053570(d).

MATHEMATICA

Table[Sum[EulerPhi[k/GCD[n, k]], {k, 1, n}], {n, 1, 59}]

PROG

(PARI) a(n) = sum(k=1, n, eulerphi(k/gcd(n, k))); \\ Michel Marcus, Feb 21 2020

CROSSREFS

Cf. A000010, A002088, A029935, A029939, A053570, A332685.

Sequence in context: A302835 A200672 A341497 * A069999 A271661 A035563

Adjacent sequences: A332683 A332684 A332685 * A332687 A332688 A332689

KEYWORD

nonn

AUTHOR

Ilya Gutkovskiy, Feb 19 2020

STATUS

approved

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Last modified January 28 03:55 EST 2023. Contains 359850 sequences. (Running on oeis4.)