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A231475 Largest integer less than 5 and coprime to n.

%I A231475 #20 Aug 27 2022 17:58:52
%S A231475 4,3,4,3,4,1,4,3,4,3,4,1,4,3,4,3,4,1,4,3,4,3,4,1,4,3,4,3,4,1,4,3,4,3,
%T A231475 4,1,4,3,4,3,4,1,4,3,4,3,4,1,4,3,4,3,4,1,4,3,4,3,4,1,4,3,4,3,4,1,4,3,
%U A231475 4,3,4,1,4,3,4,3,4,1,4,3,4,3,4,1,4,3,4,3,4,1,4,3,4,3,4,1,4,3,4
%N A231475 Largest integer less than 5 and coprime to n.
%H A231475 Antti Karttunen, <a href="/A231475/b231475.txt">Table of n, a(n) for n = 1..65537</a>
%H A231475 Wikipedia, <a href="http://en.wikipedia.org/wiki/Greatest_common_divisor">GCD</a>
%F A231475 a(2k+1) = 4 = 2*2.
%F A231475 a(2k) = 1 if 3|k, otherwise a(2k)=3. - _Jon Perry_, Nov 09 2013
%e A231475 a(1)=4 because this is the largest integer less than 5 and it's coprime to n=1.
%e A231475 a(2)=3 because 4 is not coprime to 2 but 3 is.
%e A231475 a(6)=1 because no other positive integer n<4 is coprime to 6=2*3.
%t A231475 Max[Table[If[CoprimeQ[#,d],d,0],{d,4}]]&/@Range[100] (* _Harvey P. Dale_, Aug 27 2022 *)
%o A231475 (PARI) A231475(n, m=5) = for(k=1, m, gcd(n, m-k)==1&&return(m-k));
%Y A231475 Cf. A231471 (analog for 11), A231470 (analog for 10), A231155.
%K A231475 nonn,easy
%O A231475 1,1
%A A231475 _M. F. Hasler_, Nov 09 2013