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A220627
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Prime numbers that are not Brazilian.
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14
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2, 3, 5, 11, 17, 19, 23, 29, 37, 41, 47, 53, 59, 61, 67, 71, 79, 83, 89, 97, 101, 103, 107, 109, 113, 131, 137, 139, 149, 151, 163, 167, 173, 179, 181, 191, 193, 197, 199, 223, 227, 229, 233, 239, 251, 257, 263, 269, 271, 277, 281, 283, 293, 311, 313, 317
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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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These are primes not in A085104 (Brazilian primes).
Primes that are not repunit in any base b >= 2 with three or more digits.
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LINKS
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T. D. Noe, Table of n, a(n) for n = 1..1000
Bernard Schott, Les nombres brésiliens, Quadrature, no. 76, avril-juin 2010, pages 30-38; included here with permission from the editors of Quadrature.
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MATHEMATICA
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brazBases[n_] := Select[Range[2, n - 2], Length[Union[IntegerDigits[n, #]]] == 1 &]; Select[Range[2, 1000], PrimeQ[#] && brazBases[#] == {} &] (* T. D. Noe, Dec 26 2012 *)
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PROG
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(Python)
from sympy.ntheory.factor_ import digits
from sympy import isprime, primerange
def B(n):
l=[]
for b in range(2, n - 1):
d=digits(n, b)[1:]
if max(d)==min(d): l.append(n)
return l
print([n for n in primerange(2, 1001) if not B(n)]) # Indranil Ghosh, Jun 22 2017
(PARI) isok(p) = {if (isprime(p), for (b=2, p-1, my(d=digits(p, b), md=vecmin(d)); if ((#d > 2) && (md == 1) && (vecmax(d) == 1), return (0)); ); return (1); ); } \\ Michel Marcus, Apr 30 2021
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CROSSREFS
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Cf. A085104.
Sequence in context: A044042 A175179 A040060 * A040083 A045308 A245639
Adjacent sequences: A220624 A220625 A220626 * A220628 A220629 A220630
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KEYWORD
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nonn,base
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AUTHOR
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Bernard Schott, Dec 17 2012
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STATUS
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approved
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