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A073106
Least k such that there are n primes among the numbers 2*n*x + 1 for 1 <= x <= k.
1
1, 3, 3, 11, 7, 9, 15, 22, 15, 26, 30, 28, 36, 39, 23, 53, 45, 45, 62, 61, 41, 77, 72, 66, 74, 94, 59, 93, 120, 71, 116, 124, 75, 122, 100, 104, 144, 192, 101, 155, 166, 109, 176, 189, 101, 198, 192, 140, 186, 174, 129, 242, 250, 162, 180, 231, 159, 228, 276, 162
OFFSET
1,2
LINKS
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
Sequence in context: A262528 A359685 A362154 * A309692 A107229 A302510
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Aug 19 2002
STATUS
approved