OFFSET
2,4
COMMENTS
LINKS
Martin Becker, Table of n, a(n) for n = 2..400
EXAMPLE
For n=5, m=5, there are 20 primitive polynomials over GF(5) of the form x^3+a*x^2+b*x+c. Among these, 4 polynomials have a=0: x^3+3*x+2, x^3+3*x+3, x^3+4*x+2, and x^3+4*x+3. Thus, a(5) = 4.
PROG
(PARI)
is_max_o = (x1, x0, m, e)-> {
for(i = 1, #e, if(x1^e[i] == x0, return(0))); x1^m == x0;
}
count_them = (q)-> {
z = ffprimroot(ffgen(q, 'c));
m = q^3 - 1; f = factor(m); d = #f~;
e = vector(d, i, m/f[d + 1 - i, 1]);
co = vector(q - 1, i, z^(i - 1));
r = 0;
for(a = 1, q - 1,
for(b = 1, q - 1,
p = co[1]*x^3 + co[a]*x + co[b];
x1 = Mod(x, p); x0 = x1^0;
if(is_max_o(x1, x0, m, e) && polisirreducible(p), r += 1)
)
);
r;
}
print1(count_them(2));
for(q = 3, 64, if(isprimepower(q), print1(", ", count_them(q))))
CROSSREFS
KEYWORD
nonn
AUTHOR
Martin Becker, Jun 23 2024
STATUS
approved