This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A128859 #12 Oct 11 2021 04:37:40 %S A128859 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 A128859 24,17,18,32,18,36,16,24,26,36,42,37,24,29,32,42,23,16,38,49,36,56,44, %U A128859 32,44,64,59,66,33,44,48,40,72,48,55,48,78,35,48,79,56,80,80,60,60,55 %N A128859 Let p be the n-th odd prime; a(n) is the number of primitive roots of p which are <= (p-1)/2. %D A128859 Roger Osborn, Tables of All Primitive Roots of Odd Primes Less Than 1000, Univ. Texas Press, Austin, TX, 1961, pp. 69-70. %H A128859 Amiram Eldar, <a href="/A128859/b128859.txt">Table of n, a(n) for n = 1..10000</a> %t A128859 a[n_] := Count[PrimitiveRootList[(p = Prime[n+1])], _?(# <= (p-1)/2 &)]; Array[a, 100] %Y A128859 Cf. A118818. %K A128859 nonn,easy %O A128859 1,5 %A A128859 _N. J. A. Sloane_, Apr 20 2007 %E A128859 More terms from _Don Reble_, Apr 20 2007