A232533 a(n) = Sum_{i=1...n} Sum_{j=1..i} lcm(i,j)/i.
1, 3, 7, 13, 24, 35, 57, 79, 110, 142, 198, 237, 316, 381, 455, 541, 678, 770, 942, 1058, 1209, 1376, 1630, 1781, 2042, 2278, 2552, 2789, 3196, 3417, 3883, 4225, 4614, 5024, 5476, 5812, 6479, 6994, 7544, 7996, 8817, 9269, 10173, 10784, 11425, 12186, 13268
Offset: 1
Keywords
Examples
a(3) = lcm(1,1)/1 + (lcm(2,1) + lcm(2,2))/2 + (lcm(3,1) + lcm(3,2) + lcm(3,3))/3 = 7.
Links
- Project Euler, Problem 448: Average least common multiple
Crossrefs
Cf. A057661.
Programs
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Mathematica
Table[Sum[Sum[LCM[m, k], {k, m}]/m, {m, n}], {n, 50}] (* T. D. Noe, Nov 25 2013 *) -
PARI
a(n)=sum(k=1,n,sum(b=1,k,lcm(b,k)/k));
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PARI
a(n)=sum(k=1,n,sum(m=1,k,m/gcd(m,k))); \\ Charles R Greathouse IV, Nov 25 2013
Comments