%I #23 May 03 2019 07:17:14
%S 0,2,6,20,100,600,3150,15750,78000,390000,1952500,9768750,48831250,
%T 244125000,1220625000,6103437500,30517656250,152588281250,
%U 762939062500,3814695312500,19073484375000,95367441406250,476837167968750,2384185742187500,11920928710937500
%N Number of strings of length n over Z_5 with trace 0 and subtrace 1.
%C Same as the number of strings of length n over Z_5 with trace 0 and subtrace 4.
%C Same as the number of strings of length n over GF(5) with trace 0 and subtrace 1.
%C Same as the number of strings of length n over GF(5) with trace 0 and subtrace 4.
%H Max Alekseyev, <a href="http://home.gwu.edu/~maxal/gpscripts/">PARI/GP scripts for miscellaneous math problems</a>
%H F. Ruskey, <a href="http://combos.org/TSstringZ5">Strings over Z_5 with given trace and subtrace</a>
%H F. Ruskey, <a href="http://combos.org/TSstringF5">Strings over GF(5) with given trace and subtrace</a>
%F a(n; t, s) = a(n-1; t, s) + a(n-1; t+4, s+4t+1) + a(n-1; t+3, s+3t+4) + a(n-1; t+2, s+2t+4) + a(n-1; t+1, s+t+1).
%F Empirical g.f.: 2*x^2*(50*x^5-50*x^4+5*x^3+15*x^2-7*x+1) / ((5*x-1)*(5*x^2-1)*(25*x^4-25*x^3+15*x^2-5*x+1)). - _Colin Barker_, Apr 03 2015
%Y Cf. A073963, A073965, A073966, A073967, A073968, A073969, A073970.
%K easy,nonn
%O 1,2
%A _Frank Ruskey_, Nate Kube, Aug 15 2002
%E Terms a(11) onward from _Max Alekseyev_, Apr 09 2013