triangle/triangle
Richard Guy
rkg at cpsc.ucalgary.ca
Wed Nov 21 17:33:33 CET 2001
The equation can be written as a Baskhara
(aka Pell) equation
(2n+1)^2 - c(2m+1)^2 = 1-c
I believe that this is solvable just if c
is not a non-trivial square, though the
(infinitely many) solutions don't always
come from the convergents to the continued
fraction for root c
E.g. If we try c = 7, we get the convergents
0 1 2 3 5 8 37 45 82 127 590
- - - - - - -- -- -- --- --- ...
1 0 1 1 2 3 14 17 31 48 223
none of which work, but the mediants
0+1 5+8 82+127
--- --- ------ ...
1+0 2+3 31+48
give (m,n) =
(0,0) (2,6) (39,104)
and the next one is (629,1665)
Best, R.
On Wed, 21 Nov 2001, David W. Wilson wrote:
>
> Let c = a/b where a and b are positive triangulars and c is an integer.
> Empirically, it looks as if c can take on any positive integer value
> except a square >= 4. Is this the case?
>
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