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%I #12 Oct 11 2021 04:37:40
%S 0,1,1,1,2,4,2,4,6,4,6,8,6,9,12,10,8,10,9,12,10,16,20,16,20,13,22,18,
%T 24,17,18,32,18,36,16,24,26,36,42,37,24,29,32,42,23,16,38,49,36,56,44,
%U 32,44,64,59,66,33,44,48,40,72,48,55,48,78,35,48,79,56,80,80,60,60,55
%N Let p be the n-th odd prime; a(n) is the number of primitive roots of p which are <= (p-1)/2.
%D Roger Osborn, Tables of All Primitive Roots of Odd Primes Less Than 1000, Univ. Texas Press, Austin, TX, 1961, pp. 69-70.
%H Amiram Eldar, <a href="/A128859/b128859.txt">Table of n, a(n) for n = 1..10000</a>
%t a[n_] := Count[PrimitiveRootList[(p = Prime[n+1])], _?(# <= (p-1)/2 &)]; Array[a, 100]
%Y Cf. A118818.
%K nonn,easy
%O 1,5
%A _N. J. A. Sloane_, Apr 20 2007
%E More terms from _Don Reble_, Apr 20 2007
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