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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. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
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
Sequence in context: A260753 A079237 A262060 * A013510 A013504 A230807
KEYWORD
nonn
AUTHOR
Derek Orr, Jun 04 2014
STATUS
approved

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Last modified June 25 10:28 EDT 2024. Contains 373701 sequences. (Running on oeis4.)