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A077572
Nonsquarefree numbers obtained by repeating a single digit.
1
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
OFFSET
1,1
EXAMPLE
666 and 111111111 are members but 66, 1111 etc. are not.
MATHEMATICA
Select[Flatten[Table[FromDigits[PadRight[{}, i, n]], {i, 9}, {n, 9}]], !SquareFreeQ[#]&] (* Harvey P. Dale, Jan 22 2013 *)
PROG
(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
print(list(filter(okrep, repsthru(9)))) # Michael S. Branicky, Apr 08 2021
CROSSREFS
Subsequence of A013929 and A035132.
Sequence in context: A360758 A237607 A035132 * A239520 A083807 A098128
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Nov 11 2002
EXTENSIONS
Corrected and extended by Ray Chandler, Aug 12 2003
Offset changed by Andrew Howroyd, Sep 29 2024
STATUS
approved