%I A082871
%S A082871 0,0,0,1,1,1,1,2,4
%N A082871 First component x of pairs (x,y) where x <= y and x!+y! is a square, 
               sorted on x.
%C A082871 Conjecture: the only solutions for x!+y!=n^2 (x <= y) are x=0,0,0,1,1,
               1,2,4 and y=4,5,7,4,5,7,2,5 respectively.
%o A082871 (PARI) sumfactsq(n) = { for(x=0,n, for(y=1,n, z = x!+y!; if(issquare(z),
               print1(x" ")) ) ) }
%Y A082871 Cf. A151819.
%Y A082871 Sequence in context: A128668 A038537 A120313 this_sequence A139627 A166926 
               A028573
%Y A082871 Adjacent sequences: A082868 A082869 A082870 this_sequence A082872 A082873 
               A082874
%K A082871 nonn
%O A082871 1,8
%A A082871 Cino Hilliard (hillcino368(AT)gmail.com), May 25 2003
%E A082871 Edited and corrected by Farideh Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), 
               Jul 07 2009