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 A073256 a(n) = phi(n-th composite number). 3
 2, 2, 4, 6, 4, 4, 6, 8, 8, 6, 8, 12, 10, 8, 20, 12, 18, 12, 8, 16, 20, 16, 24, 12, 18, 24, 16, 12, 20, 24, 22, 16, 42, 20, 32, 24, 18, 40, 24, 36, 28, 16, 30, 36, 32, 48, 20, 32, 44, 24, 24, 36, 40, 36, 60, 24, 32, 54, 40, 24, 64, 42, 56, 40, 24, 72, 44, 60, 46, 72, 32, 42, 60 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1200 FORMULA a(n) = A000010(A002808(n)). EXAMPLE 100th composite is 133; phi(133) = 108 = a(100). MATHEMATICA c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] Table[EulerPhi[c[w], {w, 1, 128}] With[{nn=100}, EulerPhi[#]&/@Complement[Range[2, nn], Prime[Range[ PrimePi[ nn]]]]] (* Harvey P. Dale, Apr 28 2014 *) CROSSREFS Cf. A000010, A002808, A035004, A073255. Sequence in context: A051495 A286542 A278973 * A166362 A050469 A085730 Adjacent sequences:  A073253 A073254 A073255 * A073257 A073258 A073259 KEYWORD nonn AUTHOR Labos Elemer, Jul 22 2002 STATUS approved

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Last modified May 7 20:36 EDT 2021. Contains 343652 sequences. (Running on oeis4.)