OFFSET
1,8
COMMENTS
If n is a prime other than 3, then a(n) = A000005(n+1)/2 - 1. - Robert Israel, Oct 29 2018
LINKS
Robert Israel, Table of n, a(n) for n = 1..1000
MAPLE
f:= proc(n) local x, y, z, t;
t:= 0;
for x from 1 to n do
for y from max(x, ceil(n/x)) to n do
if x*y = n then next fi;
z:= n*(x+y)/(x*y-n);
if z::integer and z>=y and z<=n then t:= t+1 fi
od od:
t
end proc:
map(f, [$1..100]); # Robert Israel, Oct 29 2018
MATHEMATICA
a[n_] := Sum[Boole[x y z/(x + y + z) == n], {x, n}, {y, x}, {z, y}];
Array[a, 100] (* Jean-François Alcover, Aug 24 2020 *)
PROG
(PARI) for(n=1, 90, print1(sum(a=1, n, sum(b=1, a, sum(c=1, b, if(a*b*c/(a+b+c)-n, 0, 1)))), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Jun 23 2002
STATUS
approved