A263875 a(n) = least positive k such that A263874(n) + 2^k is prime.

1, 2, 3, 4, 5, 8, 10, 20, 29, 955, 4583176, 9092392

Offset

1,2

Comments

A263874 gives where the records occur.

Links

Table of n, a(n) for n=1..12.

mersenneforum.org, Five or Bust - The Dual Sierpinski Problem

Prog

(PARI) a=1; forstep(n=1, 773, 2, k=1; while(!ispseudoprime(n+2^k), k++); if(k+1>a, print1(k, ", "); a=k+1));

Crossrefs

Cf. A067760, A263874.

Sequence in context: A211981 A019997 A378188 * A351702 A125157 A093327

Adjacent sequences: A263872 A263873 A263874 * A263876 A263877 A263878

Keyword

nonn,hard,more

Author

Arkadiusz Wesolowski, Oct 28 2015

Status

approved