A334053 Least b such that b^(2^n) + 1 is a Proth prime (A080076).

2, 2, 2, 2, 2, 96, 6912, 960, 16256, 2013184, 235520, 61184, 125440, 992256, 155615232, 550207488, 12192710656

Offset

0,1

Comments

Every term b is in A116882 (the prime factor 2 of b must account for more than the square root of b).

For n up to about 11, a(n) can be found with the PARI function below. From there up to n=14, you can find a(n) by filtering lists of known primes of the form b^(2^n) + 1.

Links

Table of n, a(n) for n=0..16.

Chris K. Caldwell, The Prime Pages, 12192710656^65536 + 1

Prog

(PARI) a(n) = forstep(b=2, +oo, 2, 2*valuation(b, 2)>logint(b, 2)&&ispseudoprime(b^(2^n)+1)&&return(b))

Crossrefs

Cf. A056993, A080076, A116882.

Sequence in context: A056993 A338931 A057331 * A270374 A067089 A339027

Adjacent sequences: A334050 A334051 A334052 * A334054 A334055 A334056

Keyword

more,nonn

Author

Jeppe Stig Nielsen, Sep 07 2020

Extensions

a(15) calculated by Pavel Atnashev added by Jeppe Stig Nielsen, Sep 18 2020

a(16) calculated by Pavel Atnashev added by Jeppe Stig Nielsen, Jan 05 2021

Status

approved