A072530 - OEIS

A072530

Number of primes p such that n divided by p leaves a prime remainder.

0, 0, 0, 0, 1, 0, 1, 2, 1, 1, 1, 2, 2, 2, 1, 3, 3, 3, 2, 3, 1, 3, 3, 5, 2, 4, 2, 4, 3, 4, 3, 4, 4, 3, 2, 6, 4, 5, 2, 6, 4, 6, 3, 6, 4, 5, 5, 7, 4, 6, 4, 5, 4, 8, 3, 5, 4, 7, 5, 9, 3, 7, 5, 8, 5, 7, 3, 8, 4, 8, 5, 10, 6, 7, 5, 8, 4, 9, 6, 9, 7, 8, 4, 10, 5, 7, 6, 8, 7, 12, 5, 8, 8, 8, 5, 12, 6, 10, 5, 10, 5

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OFFSET

1,8

COMMENTS

Is there any n > 6 such that a(n) =0 ?

LINKS

Table of n, a(n) for n=1..101.

EXAMPLE

a(17) = 3: there are 3 primes viz. 3, 5 and 7 which leave prime remainders on dividing 17.

MATHEMATICA

Table[Count[PrimeQ[Table[Mod[w, Prime[j]], {j, 1, PrimePi[w]}]], True], {w, 1, 256}]

CROSSREFS