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

1,1

Comments

Differs from A362147 at a(419).

Links

Table of n, a(n) for n=1..67.

Prog

(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

Crossrefs

Cf. A076467, A362147.

Sequence in context: A284837 A068937 A285316 * A362147 A361395 A329135

Adjacent sequences: A378284 A378285 A378286 * A378288 A378289 A378290

Keyword

nonn,easy

Author

Chai Wah Wu, Nov 21 2024

Status

approved