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A245657 Primes p for which none of the concatenations  p3, p9, 3p, 9p are primes. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..50.

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

Cf. A232210, A242775, A247341, A247342.

Sequence in context: A037115 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

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Last modified June 19 06:47 EDT 2019. Contains 324218 sequences. (Running on oeis4.)