login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A098026 Smallest prime p such that p+1 has exactly n distinct prime factors. 4
2, 5, 29, 389, 2309, 30029, 570569, 11741729, 300690389, 10407767369, 239378649509, 9426343036109, 304250263527209, 19835154277048109, 693386350578511589, 37508276737897976009, 2925030695773453637369 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

a(4) = 389 because 389+1 = 2*3*5*13.

MATHEMATICA

Generate[pIndex_, i_] := Module[{p2, t}, p2=pIndex; While[p2[[i]]++; Do[p2[[j]]=p2[[i]]+j-i, {j, i+1, Length[p2]}]; t=Times@@Prime[p2]; t<fact*base, AppendTo[s, t]; If[i<Length[p2], Generate[p2, i+1]]]]; fact=2; Table[pin=Range[n]; base=Times@@Prime[pin]; s={base}; Do[Generate[pin, j], {j, n}]; s=Sort[s]; noPrime=True; i=0; While[noPrime&&i<Length[s], i++; noPrime=!PrimeQ[ -1+s[[i]]]]; If[noPrime, -1, -1+s[[i]]], {n, 20}] (T. D. Noe)

CROSSREFS

Cf. A073918 (least prime p such that p-1 has exactly n distinct prime factors).

Sequence in context: A191621 A103592 A209428 * A179823 A064098 A181078

Adjacent sequences:  A098023 A098024 A098025 * A098027 A098028 A098029

KEYWORD

more,nonn

AUTHOR

Lekraj Beedassy, Sep 10 2004

EXTENSIONS

Corrected and extended by Ray Chandler, Sep 18 2004

Further corrected and extended by T. D. Noe, Dec 13 2004

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 13 00:57 EDT 2021. Contains 344980 sequences. (Running on oeis4.)