A243411 Least prime p such that p*10^n-1, p*10^n-3, p*10^n-7 and p*10^n-9 are all prime.

2, 2, 10193, 24851, 20549, 719, 22133, 230471, 46679, 432449, 114689, 227603, 305297, 61463, 1866467, 866309, 1189403, 362081, 2615783, 493433, 966353, 4154363, 6562931, 9096203, 3701627, 3128813, 20983727, 303593, 24437537, 1068491

Offset

1,1

Links

Table of n, a(n) for n=1..30.

Mathematica

lpp[n_]:=Module[{p=2, c=10^n}, While[!AllTrue[p*c-{1, 3, 7, 9}, PrimeQ], p= NextPrime[ p]]; p]; Array[lpp, 30] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jun 12 2016 *)

Prog

(Python)
import sympy
from sympy import isprime
from sympy import prime
def a(n):
..for k in range(1, 10**8):
....if isprime(prime(k)*10**n-1) and isprime(prime(k)*10**n-3) and isprime(prime(k)*10**n-7) and isprime(prime(k)*10**n-9):
......return prime(k)
n = 1
while n < 100:
..print(a(n), end=', ')
..n+=1
(PARI) a(n)=for(k=1, 10^8, if(ispseudoprime(prime(k)*10^n-1) && ispseudoprime(prime(k)*10^n-3) && ispseudoprime(prime(k)*10^n-7) && ispseudoprime(prime(k)*10^n-9), return(prime(k))))
n=1; while(n<100, print1(a(n), ", "); n++)

Crossrefs

Cf. A242564, A064432.

Sequence in context: A260753 A079237 A262060 * A013510 A013504 A230807

Adjacent sequences: A243408 A243409 A243410 * A243412 A243413 A243414

Keyword

nonn

Author

Derek Orr, Jun 04 2014

Status

approved