A378287 Numbers not of the form m^k for some k>=3. Complement of A076467.

2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 72, 73

Offset: 1

Author

Chai Wah Wu, Nov 21 2024

Keywords

• nonn
• easy

Comments

Differs from A362147 at a(419).

Crossrefs

Cf. A076467, A362147.

Programs

Python

from sympy import integer_nthroot, mobius
def A378287(n):
    def f(x): return int(n+integer_nthroot(x,4)[0]-sum(mobius(k)*(integer_nthroot(x,k)[0]+integer_nthroot(x,k<<1)[0]-2) for k in range(3,x.bit_length())))
    m, k = n, f(n)
    while m != k: m, k = k, f(k)
    return m