(In reply to re: A start!
I note that the sequence: 1,13,181,2521,35113,489061,6811741,94875313
is recorded at Sloane with reference A001770.
In the annotation, under References is the Name V. Thebault with a title that makes reference to this subject. Unfortunately I don't understand what is there but it might offer a clue.
Posted by brianjn
on 2009-12-17 23:40:11