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A220570
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Numbers that are not Brazilian numbers.
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19
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1, 2, 3, 4, 5, 6, 9, 11, 17, 19, 23, 25, 29, 37, 41, 47, 49, 53, 59, 61, 67, 71, 79, 83, 89, 97, 101, 103, 107, 109, 113, 131, 137, 139, 149, 151, 163, 167, 169, 173, 179, 181, 191, 193, 197, 199, 223, 227, 229, 233, 239, 251, 257, 263, 269, 271, 277, 281
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OFFSET
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1,2
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COMMENTS
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The terms of this sequence are:
- integer 1
- oblong semiprime 6,
- primes that are not Brazilian, they are in A220627, and,
- squares of all the primes, except 121 = (11111)_3.
So there is an infinity of integers that are not Brazilian numbers. (End)
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REFERENCES
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Pierre Bornsztein, "Hypermath", Vuibert, Exercise a35, page 7.
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LINKS
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Bernard Schott, Les nombres brésiliens, Quadrature, no. 76, avril-juin 2010, &6 page 36; included here with permission from the editors of Quadrature.
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EXAMPLE
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25 is a member because it's not possible to write 25=(mm...mm)_b where b is a natural number with 1 < b < 24 and 1 <= m < b.
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PROG
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(PARI) for(n=1, 300, c=0; for(b=2, n-2, d=digits(n, b); if(vecmin(d)==vecmax(d), c=n; break); c++); if(c==max(n-3, 0), print1(n, ", "))) \\ Derek Orr, Apr 30 2015
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CROSSREFS
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Cf. A125134 (Brazilian numbers), A190300 (composite numbers not Brazilian), A258165 (odd numbers not Brazilian), A220627 (prime numbers not Brazilian).
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KEYWORD
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nonn,easy,base
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AUTHOR
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STATUS
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approved
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