This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
[n: n in [1..500] | IsPrime(10^n + 123456789)]; // Vincenzo Librandi, Oct 12 2014
Select[Range[10^4], PrimeQ[10^# + 123456789] &] (* Robert Price, Sep 08 2019 *)
for(n=1,10^4,if(ispseudoprime(10^n + 123456789),print1(n,", ")))
[n: n in [1..500] | IsPrime(10^n+987654321)]; // Vincenzo Librandi, Oct 12 2014
Select[Range[1000], PrimeQ[10^# + 987654321] &] (* Vincenzo Librandi, Oct 12 2014 *)
for(n=1,10^4,if(ispseudoprime(10^n+987654321),print1(n,", ")))
Select[Range[10000], PrimeQ[10^# - 987654321] &] (* Robert Price, Dec 05 2019 *)
for(n=1,10^4,if(ispseudoprime(10^n-987654321),print1(n,", ")))
1 is a term because 1234567891 is prime. 2 is not a term because 12345678901 is composite (it is divisible by 857).
Select[Range@ 1400, PrimeQ[123456789*10^# + 1] &] (* Michael De Vlieger, Jan 04 2019 *)
from sympy.ntheory.primetest import isprime
for n in range(1,1000):
if isprime(123456789*10**n+1):
print(n, end=', ') # Stefano Spezia, Jan 05 2019
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