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A064950 a(n) = Sum_{i|n, j|n} lcm(i,j). 5
1, 7, 10, 27, 16, 70, 22, 83, 55, 112, 34, 270, 40, 154, 160, 227, 52, 385, 58, 432, 220, 238, 70, 830, 141, 280, 244, 594, 88, 1120, 94, 579, 340, 364, 352, 1485, 112, 406, 400, 1328, 124, 1540, 130, 918, 880, 490, 142, 2270, 267, 987, 520, 1080, 160, 1708 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = Sum_{d|n} d*tau(d^2). Multiplicative with a(p^e) = (p^(e+2) - 3*p^(e+1) + p + 1 + 2*p^(e+2)*e - 2*p^(e+1)*e)/(p-1)^2.

MATHEMATICA

a[n_]:= Sum[LCM[i, j], {i, Divisors[n]}, {j, Divisors[n]}];

Array[a, 60] (* Jean-Fran├žois Alcover, Jun 03 2019 *)

PROG

(PARI) for (n=1, 1000, d=divisors(n); a=sum(i=1, length(d), numdiv(d[i]^2)*d[i]); write("b064950.txt", n, " ", a)) \\ Harry J. Smith, Oct 01 2009

(Sage)

def A064950(n) :

    tau = sloane.A000005; D = divisors(n)

    return reduce(lambda x, y: x+y, [d*tau(d^2) for d in D])

[A064950(n) for n in (1..54)] # Peter Luschny, Sep 10 2012

CROSSREFS

Cf. A060724, A000005, A062369, A062368, A062380.

Sequence in context: A280173 A229310 A064948 * A240795 A058532 A280966

Adjacent sequences:  A064947 A064948 A064949 * A064951 A064952 A064953

KEYWORD

mult,nonn

AUTHOR

Vladeta Jovovic, Oct 28 2001

STATUS

approved

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Last modified August 21 18:38 EDT 2019. Contains 326168 sequences. (Running on oeis4.)