A245657 Primes p for which none of the concatenations p3, p9, 3p, 9p are primes.

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

Harvey P. Dale, Table of n, a(n) for n = 1..10000

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(int(p+'3')) and not isprime(int(p+'9')) and not isprime(int('3'+p)) and not isprime(int('9'+p)):
    print(int(p), end=', ') # Derek Orr, Sep 16 2014

Crossrefs

Cf. A232210, A242775, A247341, A247342.

Sequence in context: A343214 A234636 A213862 * A139921 A176807 A301369

Adjacent sequences: A245654 A245655 A245656 * A245658 A245659 A245660

Keyword

nonn,base,easy

Author

Vladimir Shevelev, Sep 13 2014

Extensions

More terms from Derek Orr, Sep 16 2014

Status

approved