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 A068211 Largest prime factor of Euler totient function phi(n). 10
 2, 2, 2, 2, 3, 2, 3, 2, 5, 2, 3, 3, 2, 2, 2, 3, 3, 2, 3, 5, 11, 2, 5, 3, 3, 3, 7, 2, 5, 2, 5, 2, 3, 3, 3, 3, 3, 2, 5, 3, 7, 5, 3, 11, 23, 2, 7, 5, 2, 3, 13, 3, 5, 3, 3, 7, 29, 2, 5, 5, 3, 2, 3, 5, 11, 2, 11, 3, 7, 3, 3, 3, 5, 3, 5, 3, 13, 2, 3, 5, 41, 3, 2, 7, 7, 5, 11, 3, 3, 11, 5, 23, 3, 2, 3, 7, 5, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 3,1 COMMENTS Smallest numbers m, such that largest prime factor of phi(m) is prime(n), a(n) is a prime number and identical to the n-th term of A035095: min{x: A068211(x) = prime(n)} = A035095(n). E.g., phi(A035095(7)) = phi(103) = 2*3*17 of which 17 = prime(7) is the largest prime factor. LINKS T. D. Noe, Table of n, a(n) for n = 3..1000 FORMULA a(n) = A006530(A000010(n)). EXAMPLE For n=46, phi(46) = 2*2*11, hence a(46) = 11. MATHEMATICA Table[FactorInteger[EulerPhi[n]][[-1, 1]], {n, 3, 100}] (* Vincenzo Librandi, Jan 04 2017 *) PROG (MAGMA) [Maximum(PrimeDivisors(EulerPhi(n))): n in [3..90]]; // Vincenzo Librandi, Jan 04 2017 (PARI) a(n) = vecmax(factor(eulerphi(n))[, 1]); \\ Michel Marcus, Jan 04 2017 CROSSREFS Cf. A000010, A006530. Cf. A035095, A035096. Sequence in context: A322868 A240975 A242166 * A236832 A089050 A167439 Adjacent sequences:  A068208 A068209 A068210 * A068212 A068213 A068214 KEYWORD nonn AUTHOR Labos Elemer, Feb 21 2002 STATUS approved

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Last modified April 15 08:18 EDT 2021. Contains 342977 sequences. (Running on oeis4.)