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A344672 a(n) = Sum_{primes p <=n} phi(floor(n/p)). 2
0, 1, 2, 2, 3, 4, 5, 5, 6, 8, 9, 7, 8, 12, 15, 13, 14, 14, 15, 13, 18, 24, 25, 17, 19, 27, 29, 23, 24, 22, 23, 23, 30, 38, 44, 28, 29, 41, 50, 38, 39, 35, 36, 34, 38, 50, 51, 37, 41, 51, 60, 52, 53, 49, 57, 49, 62, 78, 79, 43, 44, 66, 72, 58, 68, 68, 69, 65, 78, 78 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
LINKS
MATHEMATICA
a[n_] := Plus @@ EulerPhi[Floor[n/Select[Range[n], PrimeQ]]]; Array[a, 100] (* Amiram Eldar, Jul 05 2021 *)
PROG
(PARI) a(n) = my(s=0); forprime(p=2, n, s+=eulerphi(n\p)); s;
CROSSREFS
Cf. A000010, A013939 (with k instead of phi(k)), A346111 (with sigma instead).
Cf. A317625.
Sequence in context: A241730 A011884 A029070 * A360141 A354945 A112341
KEYWORD
nonn
AUTHOR
Michel Marcus, Jul 05 2021
STATUS
approved

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Last modified June 21 07:48 EDT 2024. Contains 373541 sequences. (Running on oeis4.)