

A234965


Numbers n such that 123...n  (n+1) is prime.


0




OFFSET

1,1


COMMENTS



LINKS



EXAMPLE

1234  5 = 1229 is prime so 4 is a member of this sequence.
123456  7 = 123449 is prime so 6 is a member of this sequence.


MATHEMATICA

c = 0; Do[c = n + c*10^IntegerLength[n]; If[PrimeQ[cn1)], Print@n], {n, 1700}] (* Giovanni Resta, Jan 11 2014 *)


PROG

(Python)
def Concatenate(x):
..num = ''
..for n in range(1, x+1):
....num += str(n)
..return int(num)
import sympy
from sympy import isprime
{print(x) for x in range(1, 10**3) if isprime(Concatenate(x)(x+1))}


CROSSREFS



KEYWORD

nonn,base,more


AUTHOR



EXTENSIONS



STATUS

approved



