OFFSET
1,1
COMMENTS
A Soddyian triangle is a triangle whose outer Soddy circle has degenerated into a straight line. Its side lengths are related by the equation 1/sqrt(s-c) = 1/sqrt(s-b)+1/sqrt(s-a) where the sides a <= b <= c and s is the semiperimeter. It is Heronian. The smallest side length of a primitive Soddyian triangle is given as a = n^2((m+n)^2+m^2) for integers m >= n > 0 with GCD(m, n) = 1. If this side length is squarefree, then n = 1 and (m+1)^2+m^2 has to be squarefree. a(n) is the ordered sequence of squarefree integers t of the form t = (m+1)^2+m^2. Note that t uniquely determines the primitive Soddyian triple whenever the smallest side length is squarefree.
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
F. M. Jackson, Soddyian triangles, Forum Geom. 13 (2013), 1-6.
FORMULA
Squarefree integers of the form (m+1)^2+m^2 for any integer m > 0.
EXAMPLE
a(3)=41 because the triangle with sides (41, 416, 425) is a primitive Soddyian triangles, 41 is squarefree and is the 3rd occurrence of such a squarefree integer.
MATHEMATICA
lst = {}; Do[If[SquareFreeQ[(m+1)^2+m^2], AppendTo[lst, (m+1)^2+m^2]], {m, 1, 100}]; lst
PROG
(PARI) select(issquarefree, vector(1000, m, (m+1)^2+m^2)) \\ Charles R Greathouse IV, Oct 31 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Frank M Jackson, Oct 30 2013
STATUS
approved