%I #9 Jan 04 2013 13:59:10
%S 13,28,43,58,73,93,108,123,138,153,173,188,203,208,218,233,253,268,
%T 283,298,313,333,348,363,378,393,413,428,443,448,458,473,493,508,523,
%U 538,553,573,588,603,618,637,653,668,683,688,698,717,733,748,763,778,797
%N Sum of 13 but no fewer nonzero fourth powers.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/BiquadraticNumber.html">Biquadratic Number.</a>
%t isSumQ[n_] := Do[pr = PowersRepresentations[n, k, 4]; If[k < 13, If[pr != {} , Return[False]], If[k == 13 && pr != {}, Return[True], Return[False]]], {k, 1, 13}]; Reap[For[n = 1, n <= 800, n++, If[isSumQ[n], Print[n]; Sow[n]]]][[2, 1]] (* _Jean-François Alcover_, Oct 25 2012 *)
%Y Cf. A000583, A002377, A047724, A047725.
%K nonn
%O 1,1
%A _Eric W. Weisstein_
%E More terms from Arlin Anderson (starship1(AT)gmail.com)