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%I #27 Mar 04 2018 09:38:48
%S 1,3,7,13,24,35,57,79,110,142,198,237,316,381,455,541,678,770,942,
%T 1058,1209,1376,1630,1781,2042,2278,2552,2789,3196,3417,3883,4225,
%U 4614,5024,5476,5812,6479,6994,7544,7996,8817,9269,10173,10784,11425,12186,13268
%N a(n) = Sum_{i=1...n} Sum_{j=1..i} lcm(i,j)/i.
%C Partial sums of A057661.
%H Project Euler, <a href="http://projecteuler.net/problem=448">Problem 448: Average least common multiple</a>
%e a(3) = lcm(1,1)/1 + (lcm(2,1) + lcm(2,2))/2 + (lcm(3,1) + lcm(3,2) + lcm(3,3))/3 = 7.
%t Table[Sum[Sum[LCM[m, k], {k, m}]/m, {m, n}], {n, 50}] (* _T. D. Noe_, Nov 25 2013 *)
%o (PARI) a(n)=sum(k=1,n,sum(b=1,k,lcm(b,k)/k));
%o (PARI) a(n)=sum(k=1,n,sum(m=1,k,m/gcd(m,k))); \\ _Charles R Greathouse IV_, Nov 25 2013
%Y Cf. A057661.
%K nonn
%O 1,2
%A _Zhining Yang_, Nov 25 2013
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