A073106 Least k such that there are n primes among the numbers 2*n*x + 1 for 1 <= x <= k.

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

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

Sequence in context: A359685 A362154 A379229 * A309692 A107229 A302510

Adjacent sequences: A073103 A073104 A073105 * A073107 A073108 A073109

Keyword

easy,nonn

Author

Benoit Cloitre, Aug 19 2002

Status

approved