OFFSET
1,11
LINKS
Clark Kimberling, Table of n, a(n) for n = 1..1000
EXAMPLE
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.
MATHEMATICA
t[n_] := Table[Mod[n, k], {k, 1, Floor[n/2]}]
p[n_] := DeleteDuplicates[Select[t[n], PrimeQ[#] &]]
Table[Length[p[n]], {n, 1, 200}]
PROG
(PARI) a(n) = #vecsort(select(x->isprime(x), vector(n\2, k, n % k)), , 8); \\ Michel Marcus, Feb 04 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Feb 03 2016
STATUS
approved