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A069706
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Primes with property that swapping first and last digits also gives a prime.
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6
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2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, 97, 101, 107, 113, 131, 149, 151, 157, 167, 179, 181, 191, 199, 311, 313, 337, 347, 353, 359, 373, 383, 389, 701, 709, 727, 733, 739, 743, 751, 757, 761, 769, 787, 797, 907, 919, 929, 937, 941, 953, 967, 971, 983, 991, 1009, 1013
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listen;
history;
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internal format)
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OFFSET
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1,1
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COMMENTS
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This is not the same as A007500, "palindromic" primes.
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LINKS
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EXAMPLE
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1049 and 9041 both are primes hence both are members.
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MAPLE
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swapdigs:= proc(n) local d;
d:= ilog10(n);
n + ((n mod 10)-floor(n/10^d))*(10^d-1);
end proc:
select(isprime and isprime @ swapdigs, [2, seq(2*i+1, i=1..10^4)]); # Robert Israel, Nov 11 2015
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MATHEMATICA
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Do[t = IntegerDigits[ Prime[n]]; u = t; u[[1]] = t[[ -1]]; u[[ -1]] = t[[1]]; t = FromDigits[u]; If[ PrimeQ[t], Print[ Prime[n]]], {n, 1, 300}]
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PROG
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(Python)
from sympy import prime, isprime
for i in range(5, 10**6):
p = prime(i)
s = str(p)
if isprime(int(s[-1]+s[1:-1]+s[0])):
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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