login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A107643 Numbers n such that the string 75n is prime. 0

%I

%S 1,7,17,23,29,37,41,47,49,59,61,73,77,83,89,91,109,133,149,161,167,

%T 169,181,193,209,211,217,223,227,239,253,269,277,289,307,323,329,337,

%U 347,353,367,377,389,391,401,403,407,431,437,479,503,511,521,527

%N Numbers n such that the string 75n is prime.

%e 1 is a term as 751 is prime; 2 isn't, as 752 is composite; 37 is, as 7537 is prime.

%o (Sage) is_A107643 = lambda n: is_prime(Integer('75'+str(n))) # _D. S. McNeil_, Dec 10 2010

%o (MAGMA) [ n: n in [1..700] | IsPrime(Seqint(Intseq(n) cat [5, 7])) ]; // _Vincenzo Librandi_, Feb 02 2011

%Y Cf. A107642.

%K nonn,base,less

%O 1,2

%A _Parthasarathy Nambi_, Jun 09 2005

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 July 8 07:34 EDT 2020. Contains 335513 sequences. (Running on oeis4.)