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A086165 a(n) = Card{ (x,y,z) | x < y < z and lcm(x,y,z) = n}. 3
0, 0, 0, 1, 0, 4, 0, 3, 1, 4, 0, 15, 0, 4, 4, 6, 0, 15, 0, 15, 4, 4, 0, 33, 1, 4, 3, 15, 0, 44, 0, 10, 4, 4, 4, 48, 0, 4, 4, 33, 0, 44, 0, 15, 15, 4, 0, 58, 1, 15, 4, 15, 0, 33, 4, 33, 4, 4, 0, 133, 0, 4, 15, 15, 4, 44, 0, 15, 4, 44, 0, 100, 0, 4, 15, 15, 4, 44, 0, 58, 6, 4, 0, 133, 4, 4, 4, 33, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = (A070919(n) - 3*A048691(n) + 2)/6. - Vladeta Jovovic, Dec 01 2004

MAPLE

for n from 1 to 100 do a[n] := 0:for x from 1 to n do for y from x+1 to n do for z from y+1 to n do if(lcm(x, y, z)=n) then a[n] := a[n]+1:fi:od:od:od:od:seq(a[j], j=1..200); # Sascha Kurz, Sep 22 2003

PROG

(PARI)

A048691(n) = numdiv(n^2);

A070919(n) = sumdiv(n, d, (numdiv(d)^3)*moebius(n/d));

A086165(n) = ((A070919(n)-3*A048691(n)+2)/6); \\ Antti Karttunen, May 19 2017, after Jovovic's formula

CROSSREFS

Cf. A048691, A070919, A086222.

Sequence in context: A156788 A130801 A280579 * A301408 A227290 A096303

Adjacent sequences:  A086162 A086163 A086164 * A086166 A086167 A086168

KEYWORD

nonn

AUTHOR

Yuval Dekel (dekelyuval(AT)hotmail.com), Sep 13 2003

EXTENSIONS

More terms from Sascha Kurz, Sep 22 2003

STATUS

approved

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Last modified August 6 15:44 EDT 2020. Contains 336254 sequences. (Running on oeis4.)