A098028 Smallest prime p such that p-2 is a product of exactly n distinct primes.

5, 17, 107, 1367, 15017, 285287, 6561557, 179444267, 3234846617, 100280245067, 3710369067407, 196649560572467, 8309321386330967, 307444891294245707, 24615215445537161447, 961380175077106319537, 78523577350789412776937

Offset

1,1

Links

Table of n, a(n) for n=1..17.

Example

1367 is the 4th term in the sequence because it is followed by primes 1997, 2417, 3137, 3257, ... with the property 1367-2 = 3*5*7*13, 1997-2 = 3*5*7*19, 2417-2 = 3*5*7*23, 3137-2 = 3*5*11*19, 3257-2 = 3*5*7*31, ...

Mathematica

Do[s = 3; While[ ! (Length[FactorInteger[Prime[s] - 2]] == n && Max[Last /@ FactorInteger[Prime[s] - 2]] == 1), s++ ]; Print[Prime[s]], {n, 1, 8}] (* Ryan Propper, Sep 01 2005 *)
With[{pn=PrimeNu[Prime[Range[11*10^6]]-2]}, Prime[#]&/@Flatten[Table[ Position[ pn, n, {1}, 1], {n, 8}]]] (* The program takes some time to generate the first 8 terms of the sequence *) (* Harvey P. Dale, Jan 18 2016 *)

Crossrefs

Sequence in context: A297476 A235871 A240803 * A100301 A084167 A267143

Adjacent sequences: A098025 A098026 A098027 * A098029 A098030 A098031

Keyword

nonn,hard

Author

Lekraj Beedassy, Sep 10 2004

Extensions

Extended by Ray Chandler, Sep 18 2004

One more term from Ryan Propper, Sep 01 2005

More terms from Don Reble, Apr 03 2006

Status

approved