A344772 Ordinal transform of infinitary phi, A091732.

1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 3, 2, 1, 1, 3, 1, 2, 3, 2, 1, 4, 1, 4, 2, 2, 1, 4, 1, 2, 1, 3, 2, 3, 1, 3, 4, 5, 1, 6, 1, 2, 1, 2, 1, 3, 1, 5, 2, 2, 1, 4, 2, 4, 3, 2, 1, 6, 1, 4, 2, 1, 3, 2, 1, 4, 1, 7, 1, 8, 1, 4, 5, 1, 2, 9, 1, 3, 1, 3, 1, 5, 1, 2, 1, 5, 1, 3, 2, 2, 4, 2, 3, 6, 1, 6, 2, 4, 1, 4, 1, 6, 7

Offset: 1

Author

Antti Karttunen, May 31 2021

Keywords

• nonn
• look

Comments

Number of values of k, 1 <= k <= n, with A091732(k) = A091732(n).

Links

• Antti Karttunen, Table of n, a(n) for n = 1..65537

Crossrefs

Cf. A091732, A050376, A302777.

Cf. also A081373 (ordinal transform of phi), A303756 (of Carmichael's lambda), A330739 (of unitary phi).

Programs

Mathematica

f[p_, e_] := p^(2^(-1 + Position[Reverse @ IntegerDigits[e, 2], 1]));
iphi[1] = 1; iphi[n_] := Times @@ (Flatten@(f @@@ FactorInteger[n]) - 1);
b[_] = 0;
a[n_] := a[n] = With[{t = iphi[n]}, b[t] = b[t] + 1];
Array[a, 105] (* Jean-François Alcover, Dec 27 2021, after Amiram Eldar in A091732 *)

PARI

up_to = 65537;
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; };
ispow2(n) = (n && !bitand(n,n-1));
A302777(n) = ispow2(isprimepower(n));
A091732(n) = { my(m=1); while(n > 1, fordiv(n, d, if((dA302777(n/d), m *= ((n/d)-1); n = d; break))); (m); };
v344772 = ordinal_transform(vector(up_to,n,A091732(n)));
A344772(n) = v344772[n];