A049054 Numbers k such that 10^k + 3 is prime.

1, 2, 5, 6, 11, 17, 18, 39, 56, 101, 105, 107, 123, 413, 426, 2607, 7668, 10470, 11021, 17753, 26927, 60776, 98288, 300476, 509546

Offset

1,2

Comments

A102006 is another version of the same sequence. - N. J. A. Sloane, Jan 28 2010

Verified existing 21 terms. If another term exists, it is > 39456. - Robert Price, Aug 16 2010

Links

Table of n, a(n) for n=1..25.

Makoto Kamada, Prime numbers of the form 100...003.

Henri & Renaud Lifchitz, PRP Records.

Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.

Formula

a(n) = A102006(n) + 1.

Example

5 is a term since 10^5 + 3 = 100003 is a prime.
6 is a term since 10^6 + 3 = 1000003 is a prime.

Mathematica

Do[ If[ PrimeQ[ 10^n + 3], Print[n]], {n, 0, 18000}] (* Robert G. Wilson v Jun 15 2002 *)

Prog

(PARI) is(n)=isprime(10^n + 3) \\ Charles R Greathouse IV, Apr 28 2015

Crossrefs

Cf. A102006, A159352.

Sequence in context: A180323 A103035 A088273 * A319140 A336902 A135476

Adjacent sequences: A049051 A049052 A049053 * A049055 A049056 A049057

Keyword

hard,more,nonn

Author

G. L. Honaker, Jr.

Extensions

More terms from Robert G. Wilson v, Jun 15 2002

a(16) from Ray Chandler, Oct 09 2003

a(17)-a(20) from Robert G. Wilson v, Jan 18 2005

a(21) from Jason Earls, Jan 01 2008

a(22) from Robert Price, Jan 09 2011

a(23) from Robert Price, Mar 03 2011

a(24) from Edward A. Trice, Oct 21 2012

a(25) from Paul Bourdelais, Jan 28 2021

Status

approved