A378287 - OEIS

%I #7 Nov 21 2024 22:28:03

%S 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,

%T 30,31,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,

%U 54,55,56,57,58,59,60,61,62,63,65,66,67,68,69,70,71,72,73

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

%C Differs from A362147 at a(419).

%o (Python)

%o from sympy import integer_nthroot, mobius

%o def A378287(n):

%o     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())))

%o     m, k = n, f(n)

%o     while m != k: m, k = k, f(k)

%o     return m

%Y Cf. A076467, A362147.

%K nonn,easy

%O 1,1

%A _Chai Wah Wu_, Nov 21 2024