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 A061070 Number of distinct values in the list of values of the Euler totient function {phi(j) : j=1..n}. 9
 1, 1, 2, 2, 3, 3, 4, 4, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 9, 9, 10, 10, 11, 11, 11, 11, 12, 12, 13, 13, 13, 13, 14, 14, 15, 15, 15, 15, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 19, 19, 20, 20, 20, 20, 20, 20, 21, 21, 22, 22, 22, 22, 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, 27, 27 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS T. D. Noe, Table of n, a(n) for n=1..1000 Terence Tao, Monotone non-decreasing sequences of the Euler totient function, arXiv:2309.02325 [math.NT], 2023. FORMULA a(n) = | {phi(j) : j=1..n} |. EXAMPLE From Michael De Vlieger, Sep 09 2023: (Start) a(1) = 1 since phi(1) = 1 is distinct from phi(k), k < 1. a(2) = 1 since phi(2) = phi(1). a(3) = 2 since phi(3) = 2, distinct from phi(1) = phi(2) = 1. a(4) = 2 since phi(4) = phi(3) = 2. a(5) = 3 since phi(5) = 4, distinct from phi(k), k < 5, etc. (End) MATHEMATICA nn = 120; c[_] := False; k = 0; Reap[Do[If[! c[#], k++; c[#] = True] &[EulerPhi[i]]; Sow[k], {i, nn}]][[-1, 1]] (* Michael De Vlieger, Sep 09 2023 *) PROG (Python) from sympy import totient def A061070(n): return len({totient(i) for i in range(1, n+1)}) # Chai Wah Wu, Sep 08 2023 CROSSREFS Cf. A000010. Sequence in context: A255574 A283992 A074796 * A285879 A117695 A074794 Adjacent sequences: A061067 A061068 A061069 * A061071 A061072 A061073 KEYWORD nonn AUTHOR Labos Elemer, May 28 2001 STATUS approved

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Last modified October 3 17:52 EDT 2023. Contains 365870 sequences. (Running on oeis4.)