OFFSET
1,5
COMMENTS
Conjecture: a(n) > 0 for all n > 3.
LINKS
Zhi-Wei Sun, Table of n, a(n) for n = 1..10000
EXAMPLE
a(4) = 1 since 2 is prime with 4 - 2 = 2 a term of A242754.
MATHEMATICA
p[n_]:=PrimeQ[PowerMod[n, -1, Prime[n]]]
a[n_]:=Sum[Boole[p[n-Prime[k]]], {k, 1, PrimePi[n-1]}]
Table[a[n], {n, 1, 80}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, May 23 2014
STATUS
approved