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A330747 Number of values of k, 1 <= k <= n, with A049559(k) = A049559(n), where A049559(n) = gcd(n - 1, phi(n)).

%I A330747 #10 Dec 27 2021 10:59:15
%S A330747 1,2,1,3,1,4,1,5,2,6,1,7,1,8,3,9,1,10,1,11,2,12,1,13,3,14,4,1,1,15,1,
%T A330747 16,4,17,5,18,1,19,6,20,1,21,1,22,5,23,1,24,2,25,7,2,1,26,8,27,6,28,1,
%U A330747 29,1,30,9,31,2,1,1,32,7,3,1,33,1,34,10,4,8,35,1,36,11,37,1,38,9,39,12,40,1,41,2,42,10,43,13
%N A330747 Number of values of k, 1 <= k <= n, with A049559(k) = A049559(n), where A049559(n) = gcd(n - 1, phi(n)).
%C A330747 Ordinal transform of A049559.
%H A330747 Antti Karttunen, <a href="/A330747/b330747.txt">Table of n, a(n) for n = 1..65537</a>
%t A330747 b[_] = 0;
%t A330747 a[n_] := With[{t = GCD[n-1, EulerPhi[n]]}, b[t] = b[t]+1];
%t A330747 Array[a, 105] (* _Jean-François Alcover_, Dec 27 2021 *)
%o A330747 (PARI)
%o A330747 up_to = 65537;
%o A330747 ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om,invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om,invec[i],(1+pt))); outvec; };
%o A330747 A049559(n) = gcd(n-1, eulerphi(n));
%o A330747 v330747 = ordinal_transform(vector(up_to, n, A049559(n)));
%o A330747 A330747(n) = v330747[n];
%Y A330747 Cf. A000010, A049559, A209211.
%Y A330747 Cf. also A081373, A303756, A330756.
%K A330747 nonn
%O A330747 1,2
%A A330747 _Antti Karttunen_, Dec 30 2019