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A076850
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Numbers k such that (10^k + 2)/6 is prime.
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0
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1, 2, 3, 4, 6, 10, 12, 15, 33, 55, 56, 61, 154, 201, 462, 570, 841, 848, 1297, 1357, 2008, 2628, 2848, 3111, 6877, 9162
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internal format)
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OFFSET
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1,2
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COMMENTS
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Some of the larger entries may only correspond to probable primes.
a(26) > 8000. - Jon E. Schoenfield, Dec 24 2017
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LINKS
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Table of n, a(n) for n=1..26.
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MATHEMATICA
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Select[Range[5000], PrimeQ[(10^# + 2) / 6] &] (* Vincenzo Librandi, Sep 24 2016 *)
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PROG
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(PARI) isok(n) = isprime((10^n + 2)/6); \\ Michel Marcus, Aug 28 2013
(Magma) [n: n in [0..200] |IsPrime((10^n+2) div 6)]; // Vincenzo Librandi, Sep 24 2016
(Python)
from sympy import isprime, prime, nextprime
def afind(limit, startk=1):
k, tenk = startk, 10**startk
for k in range(startk, limit+1):
if isprime((tenk + 2)//6):
print(k, end=", ")
tenk *= 10
afind(1000) # Michael S. Branicky, Feb 26 2022
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CROSSREFS
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Sequence in context: A070519 A177913 A098392 * A068482 A068499 A137172
Adjacent sequences: A076847 A076848 A076849 * A076851 A076852 A076853
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KEYWORD
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nonn,more
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AUTHOR
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Ed Pegg Jr, Nov 23 2002
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EXTENSIONS
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More terms from Jason Earls, Nov 24 2002
a(25) from Jon E. Schoenfield, Dec 23 2017
a(26) from Michael S. Branicky, Feb 27 2022
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STATUS
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approved
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