A113569 Least number, k which is a multiple of a primorial, such that p-n*k, p-(n-1)k, p-(n-2)k, ... p-2k, p-k, p, p+k, p+2k, ... p+(n-2)k, p+(n-1)k and p+n*k are all prime with p being the k-th prime.

2, 6, 720, 252420, 2053380

Offset

1,1

Links

Table of n, a(n) for n=1..5.

Example

a(1)=2 which is a multiple of a primorial.
a(2)=6 because p=13 and p-6=7 & p+6=19 all of which are prime and 6 is of the form 2*3*m, A002110.
a(3)=720 because p=5443 and p-720=4723, p-2*720=4003, p+720=6163 & p+2*720=6883 all of which are prime and 720 is of the form 2*3*5*m.
a(4)=252420 because p

Mathematica

f[n_] := Block[{p = Fold[Times, 1, Prime[ Range[ n]]]},

Crossrefs

Cf. A064403, A112530.

Sequence in context: A180492 A169661 A047690 * A252739 A178773 A046857

Adjacent sequences: A113566 A113567 A113568 * A113570 A113571 A113572

Keyword

hard,nonn

Author

Robert G. Wilson v, Sep 10 2005

Status

approved