A109602 Numbers n such that n!/(pi(n)!*2^n)+1 is prime.

1, 4, 5, 6, 7, 8, 9, 19, 20, 29, 31, 97, 113, 181, 286, 419, 485, 670, 1216

Offset

1,2

Comments

Next term, if it exists, is > 3000. - Ray Chandler, Aug 04 2005

Links

Table of n, a(n) for n=1..19.

Mathematica

f[n_] := n!/Fold[Times, 1, Range[PrimePi[n]]]*2^n + 1; Do[ If[ PrimeQ[ f[n]], Print[n]], {n, 1000}]

Crossrefs

Cf. A108894.

Sequence in context: A214419 A189481 A123977 * A084991 A356824 A099070

Adjacent sequences: A109599 A109600 A109601 * A109603 A109604 A109605

Keyword

nonn

Author

Robert G. Wilson v, Jul 18 2005

Extensions

a(19)=1216 from Ray Chandler, Aug 04 2005

Status

approved