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%I #16 Aug 31 2020 02:40:34
%S 8,16,24,27,40,48,54,56,80,81,88,104,112,120,125,135,136,152,162,168,
%T 176,184,189,208,216,232,240,248,250,264,270,272,280,296,297,304,312,
%U 328,336,343,344,351,368,375,376,378,405,408,424,432,440,456,459,464,472,488,496,512,513,520,528,536
%N Nonsquarefree numbers that are not in A177880.
%H Amiram Eldar, <a href="/A177899/b177899.txt">Table of n, a(n) for n = 1..10000</a>
%F Let B(x) be the counting function for terms not exceeding x. Then for x tends to infinity, B(x)=C*x+o(x^(0.5+eps), where C = Product_{i=p^(3^k) with prime p and k>=0}(1-1/(i^2+i+1)) - 1/zeta(2).
%p isA005836 := proc(n) convert(convert(n,base,3),set) intersect {2} ; % = {} ; end proc:
%p isA177880 := proc(n) local f; for f in ifactors(n)[2] do if not isA005836(op(2,f)) then return true; end if; end do: return false; end proc:
%p isA177899 := proc(n) not numtheory[issqrfree](n) and not isA177880(n) ; end proc:
%p for n from 1 to 1000 do if isA177899(n) then printf("%d,",n) ; end if; end do: # _R. J. Mathar_, Dec 20 2010
%t Select[Range[500], AnyTrue[(e = FactorInteger[#][[;; , 2]]), #1 > 1 &] && AllTrue[e, DigitCount[#1, 3, 2] == 0 &] &] (* _Amiram Eldar_, Aug 31 2020 *)
%Y Cf. A013929, A177880.
%K nonn
%O 1,1
%A _Vladimir Shevelev_, Dec 15 2010
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