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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
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.
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