A070209 - OEIS

%I #15 Dec 22 2017 19:11:12

%S 17,116,212,269,368,370,493,561,587,659,850,1204,1297,1582,1599,1629,

%T 1920,1988,2115,2352,2555,2574,2774,2778,3251,3473,3746,3751,4286,

%U 4298,4307,4313,4319,4330,4370,4406,5008,5251

%N Numbers n such that [A070080(n), A070081(n), A070082(n)] is an integer triangle with integer inradius.

%D Mohammad K. Azarian, Circumradius and Inradius, Problem S125, Math Horizons, Vol. 15, Issue 4, April 2008, p. 32.  Solution published in Vol. 16, Issue 2, November 2008, p. 32.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Incircle.html">Incircle</a>.

%H R. Zumkeller, <a href="/A070080/a070080.txt">Integer-sided triangles</a>

%e a(3)=212: [A070080(212), A070081(212), A070082(212)] = [5,12,13], for s = A070083(212)/2 = (5+12+13)/2 = 15: inradius = sqrt((s-5)*(s-12)*(s-13)/s) = sqrt(10*3*2/15) = sqrt(4) = 2; therefore A070200(212)=2. [Corrected by _Rick L. Shepherd_, May 15 2008]

%Y Cf. A070142, A070201, A051516.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, May 05 2002