%I A031358
%S A031358 1,2,0,2,2,0,2,2,0,2,2,0,0,2,0,2,4,0,2,0,0,4,2,0,2,2,0,2,2,0,0,2,0,0,2,
               0,
%T A031358 4,2,0,2,0,0,2,2,0,2,4,0,2,2,0,4,0,0,0,4,0,2,2,0,2,0,0,0,2,0,4,2,0,2,2,
%U A031358 0,2,2,0,0,4,0,2,2,0,4,0,0,2,0,0,2,2,0,0,4,0,2,4,0,0,2,0,2,2,0,2,0,0,2
%N A031358 Number of coincidence site lattices of index 4n+1 in lattice Z^2.
%D A031358 M. Baake, "Solution of coincidence problem...", in R. V. Moody, ed., 
               Math. of Long-Range Aperiodic Order, Kluwer 1997, pp. 9-44.
%F A031358 Dirichlet series: Product (1+p^(-s))/(1-p^(-s)); p == 1 (mod 4).
%o A031358 (PARI) t1=direuler(p=2,1200,(1+(p%4<2)*X))
%o A031358 t2=direuler(p=2,1200,1/(1-(p%4<2)*X))
%o A031358 t3=dirmul(t1,t2)
%o A031358 t4=vector(200,n,t3[4*n+1]) (and then prepend 1)
%Y A031358 Sequence in context: A123530 A161516 A123063 this_sequence A029317 A127800 
               A035692
%Y A031358 Adjacent sequences: A031355 A031356 A031357 this_sequence A031359 A031360 
               A031361
%K A031358 nonn,easy,nice
%O A031358 1,2
%A A031358 N. J. A. Sloane (njas(AT)research.att.com).
%E A031358 More terms from N. J. A. Sloane (njas(AT)research.att.com), Mar 13 2009