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A232533 a(n) = Sum_{i=1...n} Sum_{j=1..i} lcm(i,j)/i. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Partial sums of A057661.

LINKS

Table of n, a(n) for n=1..47.

Project Euler, Problem 448: Average least common multiple

EXAMPLE

a(3) = lcm(1,1)/1 + (lcm(2,1) + lcm(2,2))/2 + (lcm(3,1) + lcm(3,2) + lcm(3,3))/3 = 7.

MATHEMATICA

Table[Sum[Sum[LCM[m, k], {k, m}]/m, {m, n}], {n, 50}] (* T. D. Noe, Nov 25 2013 *)

PROG

(PARI) a(n)=sum(k=1, n, sum(b=1, k, lcm(b, k)/k));

(PARI) a(n)=sum(k=1, n, sum(m=1, k, m/gcd(m, k))); \\ Charles R Greathouse IV, Nov 25 2013

CROSSREFS

Cf. A057661.

Sequence in context: A146606 A101302 A102948 * A061263 A156209 A076276

Adjacent sequences:  A232530 A232531 A232532 * A232534 A232535 A232536

KEYWORD

nonn

AUTHOR

Zhining Yang, Nov 25 2013

STATUS

approved

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Last modified May 26 18:08 EDT 2020. Contains 334630 sequences. (Running on oeis4.)