

A056806


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


10



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

1,3


COMMENTS

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


LINKS

Table of n, a(n) for n=1..19.
Makoto Kamada, Prime numbers of the form 400...001.
Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.


FORMULA

a(n) = A101712(n1) + 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 * A270403 A119564 A132358
Adjacent sequences: A056803 A056804 A056805 * A056807 A056808 A056809


KEYWORD

more,nonn,changed


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


STATUS

approved



