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A224963 Let p = prime(n). a(n) = number of primes q less than p, such that both p+q+1 and p+q-1 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 (list; graph; refs; listen; history; text; internal format)
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+q-1 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+7-1=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

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Last modified April 25 11:43 EDT 2019. Contains 322456 sequences. (Running on oeis4.)