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%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