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A090872 a(n) is the smallest number m greater than 1 such that m^(2^k)+1 for k=0,1,...,n are primes. 10
2, 2, 2, 2, 2, 7072833120, 2072005925466, 240164550712338756 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The first five terms of this sequence correspond to Fermat primes.

LINKS

Table of n, a(n) for n=0..7.

PrimeGrid, Generalized Fermat Progression Search

Carlos Rivera, Puzzle 137. Product of primes + 1, a square, The Prime Puzzles and Problems Connection.

Carlos Rivera (ed.), Prime Puzzle # 399, The Prime Puzzles and Problems Connection.

EXAMPLE

a(5)=7072833120 because 7072833120^2^k+1 for k=0,1,2,3,4,5 are primes.

CROSSREFS

Cf. A019434, A000215.

Cf. A090873-A090875.

All solutions for fixed n: A006093 (n=0), A070689 (n=1), A070325 (n=2), A070655 (n=3), A070694 (n=4), A235390 (n=5), A335805 (n=6), A337364 (n=7).

Sequence in context: A067089 A339027 A343121 * A283472 A225538 A212355

Adjacent sequences:  A090869 A090870 A090871 * A090873 A090874 A090875

KEYWORD

nonn,more

AUTHOR

Farideh Firoozbakht, Jan 31 2004

EXTENSIONS

a(6) from Jens Kruse Andersen, May 06 2007

a(7) from Kellen Shenton, Aug 13 2020

STATUS

approved

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Last modified June 26 20:05 EDT 2022. Contains 354885 sequences. (Running on oeis4.)