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A245657
Primes p for which none of the concatenations p3, p9, 3p, 9p are primes.
1
3, 107, 113, 179, 317, 443, 487, 599, 641, 653, 751, 773, 937, 977, 991, 1021, 1087, 1103, 1187, 1201, 1213, 1217, 1301, 1409, 1427, 1439, 1483, 1553, 1559, 1579, 1609, 1637, 1693, 1747, 1777, 1787, 1789, 1861, 1949, 1987, 1993, 2081, 2129, 2239, 2281, 2287, 2293, 2351, 2393, 2477
OFFSET
1,1
LINKS
MATHEMATICA
Select[Prime[Range[400]], NoneTrue[{10#+3, 10#+9, 3*10^IntegerLength[#]+#, 9*10^IntegerLength[ #]+#}, PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 06 2020 *)
PROG
(PARI) lista(nn) = {forprime(p=2, nn, if (!isprime(eval(concat(Str(p), Str(3)))) && ! isprime(eval(concat(Str(p), Str(9)))) && ! isprime(eval(concat(Str(3), Str(p)))) && ! isprime(eval(concat(Str(9), Str(p)))), print1(p, ", ")); ); } \\ Michel Marcus, Sep 14 2014
(Python)
import sympy
from sympy import isprime
from sympy import prime
for n in range(1, 10**3):
..p = str(prime(n))
..if not isprime(p+'3') and not isprime(p+'9') and not isprime('3'+p) and not isprime('9'+p):
....print(int(p), end=', ') # Derek Orr, Sep 16 2014
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Vladimir Shevelev, Sep 13 2014
EXTENSIONS
More terms from Derek Orr, Sep 16 2014
STATUS
approved