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%I #7 Jan 11 2020 21:50:44
%S 1,1,1,2,1,1,1,3,2,1,1,2,1,1,1,4,1,3,1,2,1,1,1,4,2,2,3,2,1,1,1,5,1,1,
%T 1,5,1,1,2,3,1,2,1,2,2,1,1,6,2,4,1,3,1,7,1,3,1,1,1,2,1,1,4,6,1,1,1,2,
%U 1,1,1,8,1,2,3,2,1,2,1,5,4,2,1,3,1,1,1,3,1,3,1,2,2,1,2,9,1,4,2,6,1,1,1,5,1
%N Number of values of k, 1 <= k <= n, with A023900(k) = A023900(n), where A023900 is Dirichlet inverse of Euler totient function phi.
%C Ordinal transform of A023900.
%H Antti Karttunen, <a href="/A331178/b331178.txt">Table of n, a(n) for n = 1..65537</a>
%o (PARI)
%o up_to = 65537;
%o 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 A023900(n) = factorback(apply(p -> 1-p, factor(n)[, 1]));
%o v331178 = ordinal_transform(vector(up_to, n, A023900(n)));
%o A331178(n) = v331178[n];
%Y Cf. A000010, A023900.
%Y Cf. also A081373, A331175, A331179, A331180.
%K nonn
%O 1,4
%A _Antti Karttunen_, Jan 11 2020
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