OFFSET
1,2
COMMENTS
Conjecture: 7 <= a(n) <= 4*n^2 - 5*n + 1 for n > 1. This conjecture implies that for every odd k > 1 there exist two primes p and q < 2*k such that k = (2*p + 1)/q.
Every positive term belongs to A053176.
LINKS
Arkadiusz Wesolowski, Table of n, a(n) for n = 1..10000
PROG
(Magma) lst:=[]; for n in [2..56] do q:=1; repeat q+:=2; p:=Truncate((2*n*q-q-1)/2); until IsPrime(p) and IsPrime(q); Append(~lst, p); end for; [0] cat lst;
(PARI) a(n) = {if (n==1, return(0)); forprime(p=3, , q = (2*p+1)/(2*n-1); if ((denominator(q) == 1) && isprime(q), return (p)); ); } \\ Michel Marcus, Sep 16 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Arkadiusz Wesolowski, Sep 08 2017
STATUS
approved