A178642 Primes p such that primorial(p)/2 - 2 is not prime.

3, 29, 37, 43, 47, 59, 61, 67, 73, 79, 83, 89, 97, 101, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347

Offset

1,1

Links

Table of n, a(n) for n=1..55.

Example

3*5*7*11*13*17*19*23*29 - 2 = 43*167*450473 is composite.

Mathematica

pp=1; lst={}; Do[p=Prime[n]; pp*=p; If[ !PrimeQ[pp-2], AppendTo[lst, p]], {n, 2, 2*5!}]; lst
Transpose[Select[With[{pros=Rest[FoldList[Times, 1, Prime[Range[100]]]]}, Table[ {Prime[n], pros[[n]]}, {n, 100}]], !PrimeQ[Last[#]/2-2]&]][[1]] (* Harvey P. Dale, Mar 02 2012 *)

Crossrefs

Cf. A002110, A096177, A096547, A178641.

Sequence in context: A055062 A086174 A338518 * A125854 A167278 A341210

Adjacent sequences: A178639 A178640 A178641 * A178643 A178644 A178645

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, May 31 2010

Status

approved