%I
%S 1,2,8,15,16,18,22,32,47,48,53,58,64,70,77,78,80,94,95,96,103,106,128,
%T 138,163,199,206,256,257,266,269,311,326,330,352,358,385,397,398,401,
%U 419,421,499,512,514,538,587,599,617,622,640,672,683,757,768,770,773
%N Numbers n such that arithmetic mean of squares of the first n tribonacci numbers is an integer.
%C Could arithmetic tribonacci mean (T(0)+...+T(n1)) / n be an integer?
%C The arithmetic means are integers for the first 1, 2, 47, 53, 94, 103, 106 etc. tribonacci numbers.  _R. J. Mathar_, Aug 04 2008
%F n such that (T(0)^2+ T(1)^2+ ... + T(n1)^2) / n is an integer. T(i) = ith tribonacci number.
%Y Cf. A000073.
%Y Cf. A107239.  _R. J. Mathar_, Aug 04 2008
%K easy,nonn
%O 1,2
%A _Ctibor O. Zizka_, Jul 27 2008
%E Added 1 and 2 and extended from 32 on, _R. J. Mathar_, Aug 04 2008
