|
| |
|
|
A060324
|
|
a(n) is the minimal prime q such that n(q+1)-1 is prime, that is, the smallest prime q so that n = (p+1)/(q+1) with p prime; or a(n) = -1 if no such q exists.
|
|
6
| |
|
|
2, 2, 3, 2, 3, 2, 5, 2, 5, 2, 3, 3, 7, 2, 3, 2, 3, 2, 5, 2, 3, 5, 5, 2, 5, 3, 3, 2, 5, 2, 13, 3, 3, 2, 3, 2, 11, 2, 5, 5, 3, 3, 5, 2, 3, 2, 5, 3, 5, 2, 19, 5, 3, 7, 7, 2, 3, 2, 5, 2, 7, 11, 3, 2, 5, 2, 5, 3, 11, 5, 3, 5, 13, 5, 5, 2, 3, 2, 7, 2, 7, 5, 3, 2, 5, 2, 3, 2, 17, 2, 7, 3, 5, 2, 3, 3, 11, 2, 5, 5
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| A conjecture of Schinzel, if true, would imply that such a q always exists.
|
|
|
LINKS
| T. D. Noe, Table of n, a(n) for n=1..10000
Matthew M. Conroy, A sequence related to a conjecture of Schinzel, J. Integ. Seqs. Vol. 4 (2001), #01.1.7.
Matthew M. Conroy, Home page (listed instead of email address)
Peter Luschny, Schinzel-Sierpinski conjecture and Calkin-Wilf tree.
|
|
|
EXAMPLE
| 1 = (2+1)/(2+1), so the first term is 2; 3(2+1)-1=8 which is not prime, yet 3(3+1)-1=11 is prime (3 = (11+1)/(3+1)) so the 3rd term is 3.
|
|
|
MAPLE
| a:= proc(n) local q;
q:= 2;
while not isprime (n*(q+1)-1) do
q:= nextprime(q);
od; q
end:
seq (a(n), n=1..300); - Alois P. Heinz, Feb 11 2011
|
|
|
MATHEMATICA
| a[n_] := (q = 2; While[!PrimeQ[n*(q + 1) - 1], q = NextPrime[q]]; q); a /@ Range[100] (* From Jean-François Alcover, Jul 20 2011, after Maple prog. *)
|
|
|
CROSSREFS
| Cf. A060424. Values of p are given in A062251.
Sequence in context: A054030 A134740 A054714 * A046216 A105560 A165916
Adjacent sequences: A060321 A060322 A060323 * A060325 A060326 A060327
|
|
|
KEYWORD
| nonn,nice,easy
|
|
|
AUTHOR
| Matthew M. Conroy, Mar 29 2001
|
| |
|
|
