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A048342
Numbers k such that the concatenation of the numbers 1, 2, ..., k is squarefree.
3
1, 3, 4, 5, 7, 10, 11, 13, 14, 15, 19, 21, 22, 23, 29, 30, 31, 33, 34, 37, 38, 39, 41, 42, 43, 46, 47, 49, 51, 55, 57, 58, 59, 61, 65, 66, 67, 69, 70, 73, 74, 77, 78, 79, 82, 83, 86, 87, 91, 93, 94, 95, 97, 101, 102, 103, 105, 106, 109, 110, 111, 113, 114, 115
OFFSET
1,2
COMMENTS
Contains no multiples of 4 except 4, no terms == 0 or 8 (mod 9), and no multiples of 25. - Robert Israel, Oct 29 2024
MAPLE
filter:= n -> numtheory:-issqrfree(parse(cat($1..n))):
select(filter, [$1..50]); # Robert Israel, Oct 29 2024
CROSSREFS
Cf. A007908.
Sequence in context: A072556 A047365 A353448 * A159560 A288427 A030502
KEYWORD
nonn,hard,base
AUTHOR
Patrick De Geest, Feb 15 1999
EXTENSIONS
More terms from Sean A. Irvine, Jun 13 2021
Name edited by Robert Israel, Oct 29 2024
STATUS
approved