OFFSET
0,3
FORMULA
Conjecture:
a(2n) = A033991(2^(n-1)) = 4^n - 2^(n-1) for n >= 1;
a(2n+1) = 2^(2n+1) for n >= 1.
Conjecture from Hugo Pfoertner, Jan 09 2022: Terms starting at 3 coincide with {A156232}/8.
EXAMPLE
For n = 2, there are a(2) = 3 degree 4 polynomials of the form f(f(x)):
x^4 = f(f(x)) when f(x) = x^2 or f(x) = x^2 + 1,
x^4 + x = f(f(x)) when f(x) = x^2 + x, and
x^4 + x + 1 = f(f(x)) when f(x) = x^2 + x + 1.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Peter Kagey, Jan 03 2022
EXTENSIONS
a(0) prepended and a(11)-a(28) from Martin Ehrenstein, Jan 14 2022
STATUS
approved