%I A073997
%S A073997 1,2,3,16,76,272,1008,4096,16576,65792,261888,1048576,4197376,16781312,
%T A073997 67104768
%N A073997 Number of strings of length n over GF(4) with trace 1 and subtrace 0.
%C A073997 Same as the number of strings of length n over GF(4) with trace x and 
               subtrace 0 where x=RootOf(z^2+z+1). Same as the number of strings 
               of length n over GF(4) with trace y and subtrace 0 where y=1+x.
%H A073997 F. Ruskey <a href="http://www.theory.csc.uvic.ca/~cos/inf/trs/str/Fq/
               str_tr_subtr_F4.html">Number of strings over GF(4) of given trace 
               and subtrace</a>
%F A073997 a(n; t, s) = a(n-1; t, s) + a(n-1; t-1, s-(t-1)) + a(n-1; t-2, s-2(t-2)) 
               + a(n-1; t-3, s-3(t-3)) where t is the trace and s is the subtrace. 
               Note that all operations involving operands t or s are carried out 
               over GF(4).
%F A073997 G.f.: -(2*q^3-3*q^2+4*q-1)*q/[(1-2q)(1-4q)(1+4q^2)]. - Lawrence Sze, 
               Oct 24 2004
%Y A073997 Cf. A073995, A073996, A073998, A073999, A074000.
%Y A073997 Sequence in context: A103331 A052506 A052858 this_sequence A007118 A012572 
               A067848
%Y A073997 Adjacent sequences: A073994 A073995 A073996 this_sequence A073998 A073999 
               A074000
%K A073997 easy,nonn
%O A073997 1,2
%A A073997 Frank Ruskey, Nate Kube (fruskey(AT)cs.uvic.ca), Aug 16 2002