OFFSET
1,1
COMMENTS
Maclaurin polynomial p(2m,x) is 1 - x^2/2! + x^4/4! + ... + (-1)^m x^(2m)/(2m)!.
EXAMPLE
a(1) counts these values of 2m: 2, 6, and 10. The single positive zeros of p(2,x), p(6,x), and p(10,x) are 1.41421..., 1.56990..., and 1.57079..., respectively.
MATHEMATICA
z = 30; p[m_, x_] := Normal[Series[Cos[x], {x, 0, m }]];
t[n_] := x /. NSolve[p[n, x] == 0, x, z];
u[n_] := Select[t[n], Im[#] == 0 && # > 0 &];
v = Table[Length[u[n]], {n, 2, 100, 2}]
Table[Count[v, n], {n, 1, 10}]
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Clark Kimberling, Feb 11 2020
STATUS
approved