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A372668
a(n) = (1/phi(n)) * Sum_{j=1..n} Sum_{k=1..n} phi(n*j*k).
1
1, 9, 26, 83, 132, 404, 400, 989, 1199, 2382, 2096, 5381, 3922, 8358, 8525, 12897, 10758, 25517, 16618, 34116, 30217, 45156, 34224, 77503, 50559, 87512, 77328, 119162, 84364, 198907, 108928, 196605, 174258, 249884, 195499, 374490, 215930, 386822, 330878, 500717
OFFSET
1,2
MATHEMATICA
Table[Sum[EulerPhi[n*j*k], {j, 1, n}, {k, 1, n}]/EulerPhi[n], {n, 1, 40}] (* Vaclav Kotesovec, May 10 2024 *)
PROG
(PARI) a(n) = sum(j=1, n, sum(k=1, n, eulerphi(n*j*k)))/eulerphi(n);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, May 09 2024
STATUS
approved