A096937 Least k such that k*P(n)#/2 - 2 and k*P(n)#/2 + 2 are both primes, where P(i)= i-th prime, P(i)# = i-th primorial.

5, 3, 1, 1, 3, 1, 3, 41, 27, 3, 1, 171, 97, 19, 35, 13, 217, 57, 79, 133, 41, 219, 85, 43, 477, 205, 35, 455, 635, 275, 2081, 33, 513, 671, 427, 177, 997, 2671, 601, 123, 525, 1139, 411, 479, 363, 1311, 4685, 109, 159, 3367, 2761, 257, 161, 137, 49, 393, 3553, 1807

Offset

1,1

Links

Table of n, a(n) for n=1..58.

Example

1*2*3*5*7/2 - 2 = 103, 1*2*3*5*7/2 + 2 = 107, 103 and 107 are both primes, so for n=4, k=1.

Mathematica

Primorial[n_] := Product[Prime[i], {i, 1, n}]; f[n_] := Block[{p = Primorial[n]/2, k = 1}, While[ !PrimeQ[k*p - 2] || !PrimeQ[k*p + 2], k++ ]; k]; Table[ f[n], {n, 50}] (* Robert G. Wilson v, Aug 19 2004 *)

Crossrefs

Cf. A060256.

Sequence in context: A174965 A159671 A094853 * A097527 A204063 A132400

Adjacent sequences: A096934 A096935 A096936 * A096938 A096939 A096940

Keyword

nonn

Author

Pierre CAMI, Aug 18 2004

Extensions

More terms from Robert G. Wilson v, Aug 19 2004

Status

approved