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A109308
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Lesser emirps (primes whose digit reversal is a larger prime).
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13
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13, 17, 37, 79, 107, 113, 149, 157, 167, 179, 199, 337, 347, 359, 389, 709, 739, 769, 1009, 1021, 1031, 1033, 1061, 1069, 1091, 1097, 1103, 1109, 1151, 1153, 1181, 1193, 1213, 1217, 1223, 1229, 1231, 1237, 1249, 1259, 1279, 1283, 1381, 1399, 1409, 1429
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OFFSET
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1,1
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LINKS
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MAPLE
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read("transforms"):
option remember;
local p, R ;
if n = 1 then
return 13 ;
else
p := nextprime(procname(n-1)) ;
while true do
R := digrev(p) ;
if R> p and isprime(R) then
return p;
end if;
p := nextprime(p) ;
end do:
end if;
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MATHEMATICA
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dr[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Select[Prime[Range[1000]], PrimeQ[dr[ # ]]&&dr[ # ]>#&]
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PROG
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(PARI) isok(p) = if (isprime(p), my(q=fromdigits(Vecrev(digits(p)))); (p < q) && isprime(q)); \\ Michel Marcus, Sep 07 2021
(Python)
from sympy import isprime, primerange
def ok(p): revp = int(str(p)[::-1]); return p < revp and isprime(revp)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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