OFFSET
1,2
LINKS
Robert Israel, Table of n, a(n) for n = 1..2500
MAPLE
f:= proc(n) local x, t;
t:= 0;
for x from 1 do
if isprime(2*n*x+1) then
t:= t+1;
if t=n then return x fi
fi
od
end proc:
map(f, [$1..100]); # Robert Israel, Jul 09 2020
PROG
(PARI) a(n)=if(n<0, 0, s=1; while(sum(k=1, s, isprime(2*k*n+1))<n, s++); s)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Aug 19 2002
STATUS
approved