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PROJECT EULER · #0311

Biclinic Integral Quadrilaterals

Statement only · UnsolvedOriginal problem ↗

ABCD is a convex, integer sided quadrilateral with 1AB<BC<CD<AD.
BD has integer length. O is the midpoint of BD. AO has integer length.
We'll call ABCD a biclinic integral quadrilateral if AO=COBO=DO.

For example, the following quadrilateral is a biclinic integral quadrilateral:
AB=19, BC=29, CD=37, AD=43, BD=48 and AO=CO=23.

0311_biclinic.gif

Let B(N) be the number of distinct biclinic integral quadrilaterals ABCD that satisfy AB2+BC2+CD2+AD2N.
We can verify that B(10000)=49 and B(1000000)=38239.

Find B(10000000000).

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