OFFSET
1,1
LINKS
Pierre CAMI, Table of n, a(n) for n = 1..12250
EXAMPLE
2*(2+2)-1=7 prime so a(1)=2 as prime(1)=2;
2*(2+3)-1=9 composite; 3*(3+3)-1=17 prime so a(2)=3 as prime(2)=3.
PROG
(PARI) a(n) = {my(pn=prime(n), p=2); while (!isprime(p*(p+pn)-1), p = nextprime(p+1)); p; } \\ Michel Marcus, Sep 24 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Pierre CAMI, Aug 12 2008
EXTENSIONS
Name edited by Michel Marcus, Sep 24 2019
STATUS
approved