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A372969
a(n) = Sum_{1 <= x_1, x_2, ... , x_n <= n} n/gcd(x_1, x_2, ... , x_n, n).
2
1, 7, 79, 991, 15621, 277495, 5764795, 133955071, 3486666301, 99951163687, 3138428376711, 106980008889391, 3937376385699277, 155563347996105679, 6568408050364922499, 295145653362359140351, 14063084452067724990993, 708233993284902846818911
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OFFSET
1,2
LINKS
Seiichi Manyama,
Table of n, a(n) for n = 1..385
FORMULA
a(n) = Sum_{d|n} mu(n/d) * n/d * sigma_{n+1}(d).
a(n) = Sum_{1 <= x_1, x_2, ... , x_n <= n} ( gcd(x_1, x_2, ... , x_{n-1}, n)/gcd(x_1, x_2, ... , x_n, n) )^n.
PROG
(PARI) a(n) = sumdiv(n, d, moebius(n/d)*n/d*sigma(d, n+1));
CROSSREFS
Main diagonal of
A372968
.
Cf.
A108223
.
Sequence in context:
A127890
A198973
A127859
*
A387928
A014293
A176792
Adjacent sequences:
A372966
A372967
A372968
*
A372970
A372971
A372972
KEYWORD
nonn
AUTHOR
Seiichi Manyama
, May 18 2024
STATUS
approved
