A056806 Numbers n such that 4*10^n + 1 is prime.

0, 1, 2, 3, 13, 229, 242, 309, 957, 1473, 1494, 3182, 3727, 4177, 23210, 25719, 32835, 36990, 103958, 789955, 1038890

Offset

1,3

Comments

Some of the results were computed using the PrimeFormGW (PFGW) primality-testing program. - Hugo Pfoertner, Nov 14 2019

Links

Table of n, a(n) for n=1..21.

Makoto Kamada, Prime numbers of the form 400...001.

Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.

Formula

a(n) = A101712(n-1) + 1.

Mathematica

Do[ If[ PrimeQ[ 4*10^n + 1], Print[ n ]], {n, 0, 30000}]

Prog

(PARI) is(n)=isprime(4*10^n+1) \\ Charles R Greathouse IV, Feb 17 2017

Crossrefs

Cf. A056797 (9*10^n+1 is prime), A101712.

Sequence in context: A113494 A139520 A132535 * A376058 A270403 A119564

Adjacent sequences: A056803 A056804 A056805 * A056807 A056808 A056809

Keyword

more,nonn

Author

Robert G. Wilson v, Aug 22 2000

Extensions

a(12)-a(16) using PrimeForm from Hugo Pfoertner, Jul 08 2004

32835 from Ray Chandler, Aug 30 2010

36990 from Peter Benson, Aug 23 2003 confirmed as next term by Ray Chandler, Sep 07 2010

103958 from Peter Benson, Dec 31 2004 confirmed as next term by Ray Chandler, Feb 18 2012

a(20)-a(21) from Kamada data by Tyler Busby, May 03 2024

Status

approved