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 A131195 Nonprime record values of Euler's totient function (A000010): 1 and composite n such that phi(n) is greater than all smaller composites. 1

%I

%S 1,4,8,9,15,21,25,35,49,65,77,85,91,115,119,121,143,161,169,187,203,

%T 209,221,247,253,287,289,319,323,341,361,391,403,437,451,473,481,493,

%U 517,527,529,583,589,611,629,649,667,689,697,703,713,731,767,779,799,817

%N Nonprime record values of Euler's totient function (A000010): 1 and composite n such that phi(n) is greater than all smaller composites.

%C Since phi(p) = p - 1, allowing prime numbers in this sequence would make it A006005, the primes with a 1 replacing the initial 2.

%C Number of terms < 10^k, k=1,2,3,...: 4, 13, 61, 310, 1628, 9029, 51207, 295132, ..., . _Robert G. Wilson v_, Feb 19 2019

%H Robert G. Wilson v, <a href="/A131195/b131195.txt">Table of n, a(n) for n = 1..10000</a>

%e a(3) = 8 because phi(8) = 4, which is greater than phi(4) = phi(6) = 2. (phi(5) = 4 and phi(7) = 6 are ignored because 5 and 7 are prime).

%t htcList = {1}; i = 4; currMax = 1; searchMax = 1000; While[i < searchMax, If[Not[PrimeQ[i]] && EulerPhi[i] > currMax, htcList = {htcList, i}; currMax = EulerPhi[i]]; i++ ]; Flatten[htcList]

%Y Cf. A000010, A000040, A006005.

%K easy,nonn

%O 1,2

%A _Alonso del Arte_, Oct 20 2007

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Last modified June 19 23:01 EDT 2019. Contains 324222 sequences. (Running on oeis4.)