%I A000925
%S A000925 1,2,1,0,2,2,0,0,1,2,2,0,0,2,0,0,2,2,1,0,2,0,0,0,0,4,2,0,0,2,0,0,1,0,2,
               0,2,2,0,
%T A000925 0,2,2,0,0,0,2,0,0,0,2,3,0,2,2,0,0,0,0,2,0,0,2,0,0,2,4,0,0,2,0,0,0,1,2,
               2,0,0,
%U A000925 0,0,0,2,2,2,0,0,4,0,0,0,2,2,0,0,0,0,0,0,2,1,0,4
%N A000925 Number of ordered ways of writing n as a sum of 2 squares of nonnegative 
               integers.
%D A000925 A. Das and A. C. Melissinos, Quantum Mechanics: A Modern Introduction, 
               Gordon and Breach, 1986, p. 47.
%D A000925 E. Grosswald, Representations of Integers as Sums of Squares. Springer-Verlag, 
               NY, 1985.
%H A000925 T. D. Noe, <a href="b000925.txt">Table of n, a(n) for n=0..10000</a>
%H A000925 <a href="Sindx_Su.html#ssq">Index entries for sequences related to sums 
               of squares</a>
%F A000925 Coefficient of q^k in (1/4)*(1 + theta_3(0, q))^2.
%F A000925 a(A001481(n))>0; a(A022544(n))=0. - Benoit Cloitre (benoit7848c(AT)orange.fr), 
               Apr 20 2003
%o A000925 (PARI) a(n)=sum(i=0,n,sum(j=0,n,if(i^2+j^2-n,0,1)))
%Y A000925 Sequence in context: A025253 A112178 A134663 this_sequence A003985 A157237 
               A065676
%Y A000925 Adjacent sequences: A000922 A000923 A000924 this_sequence A000926 A000927 
               A000928
%K A000925 nonn,nice
%O A000925 0,2
%A A000925 Jacques Haubrich (jhaubrich(AT)freeler.nl)