This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A088274 Numbers n such that 10^n + 7 is prime. 22
 1, 2, 4, 8, 9, 24, 60, 110, 134, 222, 412, 700, 999, 1383, 5076, 5543, 6344, 14600, 15093, 21717, 23636, 30221, 50711 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS No others less than 59500. No other terms <= 100,000. - Robert Price, Mar 03 2011 a(24) > 2*10^5. - Robert Price, Nov 09 2015 LINKS G. L. Honaker, Jr. and Chris Caldwell, eds., Prime Curios! Makoto Kamada, Prime numbers of the form 100...007. Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers. FORMULA a(n) = A102007(n) + 1. EXAMPLE 8 is a member since 10^8 + 7 = 100000007 is a prime. MATHEMATICA Do[ If[ PrimeQ[ 10^n + 7], Print[n]], {n, 0, 10000}] (* Robert G. Wilson v, Dec 16 2004 *) PROG (PARI) is(n)=isprime(10^n + 7) \\ Charles R Greathouse IV, Apr 29 2015 CROSSREFS Cf. A088275, A049054, A102007, A159031. Sequence in context: A046685 A248741 A140141 * A118418 A074810 A028984 Adjacent sequences:  A088271 A088272 A088273 * A088275 A088276 A088277 KEYWORD nonn AUTHOR Amarnath Murthy, Sep 28 2003 EXTENSIONS a(7)-a(14) from Ray Chandler, Oct 09 2003 a(15)-a(19) from Robert G. Wilson v, Jan 18 2005 Corrected and extended by Jason Earls, Nov 27 2007 and Dec 07 2007. (14600 was missing and 23636 and 50711 are new. These are presently only probable primes, found with WinPFGW.) Missing term 30221 added by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 15 00:30 EST 2019. Contains 329988 sequences. (Running on oeis4.)