A357369 a(n) is the first prime p such that (p+q)/(2*n) is prime, where q is the next prime after p.

3, 5, 11, 13, 11, 19, 53, 17, 29, 467, 59, 23, 41, 29, 173, 31, 197, 4877, 59, 41, 151, 67, 71, 47, 751, 79, 53, 661, 59, 89, 61, 97, 101, 103, 71, 109, 73, 193, 113, 199, 461, 83, 1361, 223, 137, 3331, 139, 2297, 149, 101, 257, 1531, 107, 163, 1621, 397, 751, 997, 113, 7741, 181, 313, 191, 193

Offset

2,1

Links

Robert Israel, Table of n, a(n) for n = 2..10000

Example

a(4) = 11 because (11+13)/(2*4) = 3 is prime, and no smaller prime works.

Maple

V:= Vector(100): count:= 0:
q:= 3:
while count < 99 do
  p:= q; q:= nextprime(q);
  m:= (p+q)/2;
  for r in numtheory:-factorset(m) do
    v:= m/r;
    if v <= 100 and V[v] = 0 then
      count:= count+1; V[v]:= p;
    fi
  od
od:
convert(V[2..100], list);

Crossrefs

Cf. A357373.

Sequence in context: A309426 A115398 A014597 * A130603 A069977 A284795

Adjacent sequences: A357366 A357367 A357368 * A357370 A357371 A357372

Keyword

nonn

Author

Robert Israel, Sep 25 2022

Status

approved