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
Keywords
Examples
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.
Crossrefs
Cf. A060256.
Programs
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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 *)
Extensions
More terms from Robert G. Wilson v, Aug 19 2004