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
Links
- Makoto Kamada, Prime numbers of the form 400...001.
- Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.
Programs
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Mathematica
Do[ If[ PrimeQ[ 4*10^n + 1], Print[ n ]], {n, 0, 30000}] -
PARI
is(n)=isprime(4*10^n+1) \\ Charles R Greathouse IV, Feb 17 2017
Formula
a(n) = A101712(n-1) + 1.
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
Comments