login
This site is supported by donations to The OEIS Foundation.

 

Logo

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!)
A195905 Primes of the form 10 * n^2 + 7. 2
7, 17, 47, 97, 167, 257, 367, 647, 1217, 1447, 1697, 2897, 3617, 4007, 5297, 6257, 7297, 9007, 10247, 12967, 13697, 14447, 15217, 16007, 26017, 28097, 29167, 32497, 33647, 36007, 37217, 38447, 42257 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

First seven numbers of the form 10 * n^2 + 7 are prime numbers. They are called Trotter primes by Terrel Trotter Jr. There are 735 Trotter primes less than 10^8.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..5000

T. Trotter, Trotter numbers and Trotter primes [Warning: As of March 2018 this site appears to have been hacked. Proceed with great caution. The original content should be retrieved from the Wayback machine and added here. - N. J. A. Sloane, Mar 29 2018]

MATHEMATICA

Select[Table[10n^2+7, {n, 0, 500}], PrimeQ] (* Vincenzo Librandi, Dec 04 2011 *)

Select[(10*Range[0, 70]^2+7), PrimeQ] (* Harvey P. Dale, Dec 11 2018 *)

PROG

(MAGMA) [a: n in [0..300] | IsPrime(a) where a is 10*n^2+7]; // Vincenzo Librandi, Dec 05 2011

CROSSREFS

Cf. A000040, A061722.

Sequence in context: A179031 A107178 A061722 * A104164 A192244 A110097

Adjacent sequences:  A195902 A195903 A195904 * A195906 A195907 A195908

KEYWORD

nonn,easy

AUTHOR

Kausthub Gudipati, Sep 25 2011

EXTENSIONS

7 inserted by Omar E. Pol, Oct 03 2011

Restored the primitive offset by Vincenzo Librandi, Dec 04 2011

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 10 14:27 EST 2019. Contains 329896 sequences. (Running on oeis4.)