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A236454 Smallest number not dividing n^2.

%I A236454 #21 Jan 14 2024 02:25:44
%S A236454 2,3,2,3,2,5,2,3,2,3,2,5,2,3,2,3,2,5,2,3,2,3,2,5,2,3,2,3,2,7,2,3,2,3,
%T A236454 2,5,2,3,2,3,2,5,2,3,2,3,2,5,2,3,2,3,2,5,2,3,2,3,2,7,2,3,2,3,2,5,2,3,
%U A236454 2,3,2,5,2,3,2,3,2,5,2,3,2,3,2,5,2,3,2
%N A236454 Smallest number not dividing n^2.
%C A236454 Differs from A053669, "smallest prime not dividing n", for the first time at n=210, where a(210)=8, while A053669(210)=11. A235921 lists all n for which a(n) differs from A053669(n).
%C A236454 Differs from A214720 at n=2, 210, 630, 1050, 1470, 1890, 2310,.... - _R. J. Mathar_, Mar 30 2014
%H A236454 Antti Karttunen, <a href="/A236454/b236454.txt">Table of n, a(n) for n = 1..10000</a>
%F A236454 a(n) = A007978(A000290(n)) = A007978(n^2).
%F A236454 a(n) = A235918(n)+1.
%F A236454 Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = Sum_{k>=0} 1/A019554(A003418(k)) = 2.91240643793540602415... . - _Amiram Eldar_, Jan 14 2024
%p A236454 A236454 := proc(n)
%p A236454     for m from 2 do
%p A236454         if modp(n^2,m) <> 0 then
%p A236454             return m;
%p A236454         end if;
%p A236454     end do:
%p A236454 end proc:# _R. J. Mathar_, Mar 30 2014
%t A236454 Join[{2,3},Table[Complement[Range[n],Divisors[n^2]][[1]],{n,3,90}]] (* _Harvey P. Dale_, Mar 18 2018 *)
%o A236454 (Scheme) (define (A236454 n) (A007978 (A000290 n)))
%Y A236454 One more than A235918.
%Y A236454 Cf. A003418, A019554.
%Y A236454 Cf. also A000290, A007978, A053669, A235921.
%K A236454 nonn
%O A236454 1,1
%A A236454 _Antti Karttunen_, Jan 26 2014