

A224963


Let p = prime(n). a(n) = number of primes q less than p, such that both p+q+1 and p+q1 are primes.


0



0, 0, 0, 1, 1, 1, 1, 1, 2, 1, 2, 2, 2, 2, 1, 2, 2, 3, 2, 3, 1, 4, 2, 3, 5, 4, 3, 3, 5, 3, 6, 6, 4, 7, 3, 5, 5, 4, 5, 6, 4, 8, 4, 3, 4, 6, 6, 6, 3, 5, 5, 7, 6, 6, 2, 4, 6, 5, 2, 6, 5, 5, 5, 5, 3, 3, 8, 5, 4, 8, 4, 7, 4, 7, 7, 4, 7, 3, 5, 8, 9, 9, 6, 6, 7
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OFFSET

1,9


LINKS

Table of n, a(n) for n=1..85.


EXAMPLE

For n=3, p=5, there are no primes q(<5) such that both 5+q+1 and 5+q1 are primes and hence a(3)=0. Also for n=5, p=11, there is a(5)=1 solution 7 since 11+7+1=19, 11+71=17.


MATHEMATICA

Table[p = Prime[n]; c = 0; i = 1; While[i < n, p1 = p + Prime[i]; If[PrimeQ[p1 + 1] && PrimeQ[p1  1], c = c + 1]; i++]; c, {n, 85}]


CROSSREFS

Cf. A224748, A224908.
Sequence in context: A230643 A163367 A057226 * A073810 A055255 A057768
Adjacent sequences: A224960 A224961 A224962 * A224964 A224965 A224966


KEYWORD

nonn


AUTHOR

Jayanta Basu, Apr 21 2013


STATUS

approved



