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A323784
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Prime numbers such that the reverse of the balanced ternary representation is neither prime nor a negated prime.
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1
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3, 19, 23, 41, 47, 67, 79, 97, 107, 109, 113, 127, 131, 151, 157, 167, 191, 197, 211, 227, 229, 239, 251, 257, 271, 281, 283, 293, 307, 317, 337, 349, 359, 397, 409, 419, 431, 433, 439, 461, 463, 491, 503, 521, 523, 557, 563, 571, 577, 587, 593, 617, 619, 631, 641, 647, 653, 659, 661, 673, 683, 701, 733, 743, 769, 787, 797
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OFFSET
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1,1
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LINKS
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EXAMPLE
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79 is a term:
79 is +00-+ in balanced ternary notation
+00-+ reversed is +-00+
+-00+ is 55 in balanced ternary notation
55 prime factors are 5 and 11
Therefore 55 is not prime.
Therefore the prime number 79 "warps" to the nonprime number 55.
This operation is reversible: 55 "warps" to 79.
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PROG
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(Python) See links
(PARI) d3(n) = if ((n%3)==2, n\3+1, n\3);
m3(n) = if ((n%3)==2, -1, n % 3);
t(n) = if (n==0, [0], if (abs(n) == 1, [n], concat(m3(n), t(d3(n)))));
f(n) = subst(Pol(Vec(t(n))), x, 3);
isok(n) = isprime(n) && !isprime(abs(f(n))); \\ Michel Marcus, Jan 29 2019
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CROSSREFS
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Complement of A323782 among primes.
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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