OFFSET
1,2
COMMENTS
Same as the number of strings of length n over Z_5 with trace 0 and subtrace 4.
Same as the number of strings of length n over GF(5) with trace 0 and subtrace 1.
Same as the number of strings of length n over GF(5) with trace 0 and subtrace 4.
LINKS
FORMULA
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).
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
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Frank Ruskey, Nate Kube, Aug 15 2002
EXTENSIONS
Terms a(11) onward from Max Alekseyev, Apr 09 2013
STATUS
approved