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%I #8 Feb 11 2016 08:09:20
%S 0,0,0,0,0,0,0,1,0,1,2,1,1,1,1,1,3,2,2,1,2,1,4,2,3,2,4,2,4,2,3,2,3,2,
%T 5,2,5,3,4,3,6,2,5,2,5,2,6,2,5,3,6,3,7,3,6,3,7,4,8,3,7,4,7,3,8,2,8,4,
%U 7,4,9,3,8,4,8,4,9,2,9,5,8,5,9,3,8,4
%N Number of distinct primes (n mod k) for k=1..floor(n/2).
%H Clark Kimberling, <a href="/A268372/b268372.txt">Table of n, a(n) for n = 1..1000</a>
%e For k=1..15, the numbers (31 mod k) are 0, 1, 1, 3, 1, 1, 3, 7, 4, 1, 9, 7, 5, 3, 1; the primes are 3,3,7,7,5,3, so that a(31) = 3.
%t t[n_] := Table[Mod[n, k], {k, 1, Floor[n/2]}]
%t p[n_] := DeleteDuplicates[Select[t[n], PrimeQ[#] &]]
%t Table[Length[p[n]], {n, 1, 200}]
%o (PARI) a(n) = #vecsort(select(x->isprime(x), vector(n\2, k, n % k)),,8); \\ _Michel Marcus_, Feb 04 2016
%Y Cf. A266714, A266715.
%K nonn,easy
%O 1,11
%A _Clark Kimberling_, Feb 03 2016
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