

A246920


The number of distinct lengths of nontrivial integral cevians of an equilateral triangle of side n that divide an edge into two integral parts.


4



0, 0, 1, 0, 2, 1, 2, 2, 2, 2, 2, 1, 2, 2, 5, 4, 2, 2, 2, 2, 5, 2, 2, 5, 4, 2, 3, 2, 2, 5, 2, 6, 5, 2, 8, 2, 2, 2, 5, 8, 2, 5, 2, 2, 8, 2, 2, 9, 4, 4, 5, 2, 2, 3, 8, 8, 5, 2, 2, 5, 2, 2, 8, 8, 8, 5, 2, 2, 5, 8, 2, 8, 2, 2, 9, 2, 8, 5, 2, 14, 4, 2, 2, 5, 8, 2
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OFFSET

1,5


COMMENTS

A cevian is a line segment which joins a vertex of a triangle with a point on the opposite side (or its extension).
A nontrivial cevian is one that does not coincide with a side of the triangle.
For an equilateral triangle of side n, the lengths of its cevians are the values of y in the solutions to x^2y^2n*x+n^2=0.


LINKS



EXAMPLE

a(15) = 5 because cevians of an equilateral triangle of side 15 have length 13, 21, 35, 57 or 169.


PROG

(PARI)
\\ Returns the number of cevians of an equilateral triangle of side n.
count(n) = {
s=[];
n=12*n^2;
fordiv(n, f,
g=n\f;
if(f<=g && (f+g)%2==0,
x=(f+g)\2;
if(x%4==0,
s=concat(s, x\4)
)
)
);
Colrev(s)~
}
vector(100, n, #count(n)1)


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



