A341713 revision #38
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A341713
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Indices of Ennesrem primes: k such that A004094(k)-1 is prime.
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1
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OFFSET
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1,1
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COMMENTS
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Reverse(2^k) - 1 is prime.
Is this sequence infinite?
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LINKS
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EXAMPLE
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13 is a term, since 2^13 = 8192 -> 2918 -> 2917, which is prime.
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PROG
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(PARI) for(n=1, 10000, my(pe=fromdigits(Vecrev(digits(2^n)))-1); if(ispseudoprime(pe), print1(n, ", "))) \\ Hugo Pfoertner, Feb 20 2021
(Python)
from sympy import isprime
def ok(k): return isprime(int(str(2**k)[::-1]) - 1)
for k in range(1, 2*10**3):
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CROSSREFS
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KEYWORD
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nonn,base,more
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AUTHOR
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EXTENSIONS
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STATUS
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editing
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