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A077572
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Nonsquarefree numbers obtained by repeating a single digit.
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1
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4, 8, 9, 44, 88, 99, 333, 444, 666, 888, 999, 4444, 8888, 9999, 44444, 88888, 99999, 333333, 444444, 666666, 777777, 888888, 999999, 4444444, 8888888, 9999999, 44444444, 88888888, 99999999, 111111111, 222222222, 333333333, 444444444
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listen;
history;
text;
internal format)
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OFFSET
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0,1
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LINKS
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EXAMPLE
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666 and 111111111 are members but 66, 1111 etc. are not.
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MATHEMATICA
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Select[Flatten[Table[FromDigits[PadRight[{}, i, n]], {i, 9}, {n, 9}]], !SquareFreeQ[#]&] (* Harvey P. Dale, Jan 22 2013 *)
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PROG
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(Python)
from sympy.ntheory.factor_ import core
def repsthru(maxd):
yield from (int(di*d) for d in range(1, maxd+1) for di in "123456789")
def okrep(r): return r > 3 and core(r, 2) != r
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CROSSREFS
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KEYWORD
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base,easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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