login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A128887 Numbers n such that the number formed by the concatenation of the consecutive integers from 5 to n is prime. 0
5, 17, 71, 99, 123 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Primes of this form are rare. 2 and 5 are the only beginning numbers less than 100 that form more than 2 primes for all ending numbers less than 1000.
LINKS
EXAMPLE
The 2nd entry forms the number 567891011121314151617 which is prime.
PROG
(PARI) consecprimes(n, m) = { local(a, x, y); a=""; for(x=m, n, a=concat(a, Str(x)); y=eval(a); if(ispseudoprime(y), print(x", "y) ) ) }
CROSSREFS
Sequence in context: A249015 A273852 A146511 * A149708 A149709 A149710
KEYWORD
more,nonn,base
AUTHOR
Cino Hilliard, Apr 19 2007
EXTENSIONS
Edited by Charles R Greathouse IV, Apr 25 2010
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 14:21 EDT 2024. Contains 371254 sequences. (Running on oeis4.)