# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a300476 Showing 1-1 of 1 %I A300476 #7 Apr 16 2018 09:45:04 %S A300476 2,7,8,17,18,23,28,32,50,63,68,72,82,92,97,98,103,112,122,128,137,153, %T A300476 162,175,177,178,200,207,242,252,257,272,288,303,328,337,338,343,367, %U A300476 368,369,388,392,393,412,417,425,433,448,450,478,487,488,503,512,548,567,575 %N A300476 Numbers the square of which can be written as a sum of four nonzero bi-quadratics. %C A300476 Numbers w which can be expressed as w^2 = x^4 +y^4 +z^4 +t^4 with x,y,z,t >0. Values that have more than one representation (w=63, 153, 207, 252,...) are listed only once. %H A300476 A. Alvarado, J.-J. Delorme, On the diophantine equation x^4+y^4+z^4+t^4=w^2, J. Int. Seq. 17 (2014) # 14.11.5. %e A300476 2^2 = 1^4 +1^4 +1^4 +1^4. 7^2 = 1^4 +2^4 +2^4 +2^4. 8^2 = 2^4 +2^4 +2^4 +2^4. 17^2 = 1^2 +2^4 +2^4 +4^4. 18^2=3^4 +3^4 +3^4 +3^4. 23^2 = 1^2 +2^4 +4^4 +4^4. %K A300476 nonn %O A300476 1,1 %A A300476 _R. J. Mathar_, Mar 06 2018 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE