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A112736
Numbers whose square is exclusionary.
6
2, 3, 4, 7, 8, 9, 17, 18, 24, 29, 34, 38, 39, 47, 53, 54, 57, 58, 59, 62, 67, 72, 79, 84, 92, 94, 157, 158, 173, 187, 192, 194, 209, 237, 238, 247, 253, 257, 259, 307, 314, 349, 359, 409, 437, 459, 467, 547, 567, 612, 638, 659, 672, 673, 689, 712, 729, 738, 739, 749
OFFSET
1,1
COMMENTS
The number m with no repeated digits has an exclusionary square m^2 if the latter is made up of digits not appearing in m. For the corresponding exclusionary squares see A112735.
a(49) = 567 and a(68) = 854 are the only two numbers k such that the equation k^2 = m uses only once each of the digits 1 to 9 (reference David Wells). Exactly: 567^2 = 321489, and, 854^2 = 729316. - Bernard Schott, Dec 20 2021
REFERENCES
H. Ibstedt, Solution to Problem 2623, "Exclusionary Powers", pp. 346-9, Journal of Recreational Mathematics, Vol. 32 No.4 2003-4 Baywood NY.
David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Revised Edition, 1997, page 144, entry 567.
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..142 (full sequence)
EXAMPLE
409^2 = 167281 and the square 167281 is made up of digits not appearing in 409, hence 409 is a term.
MATHEMATICA
Select[Range[1000], Intersection[IntegerDigits[ # ], IntegerDigits[ #^2]] == {} && Length[Union[IntegerDigits[ # ]]] == Length[IntegerDigits[ # ]] &] - Tanya Khovanova, Dec 25 2006
CROSSREFS
This is a subsequence of A029783 (Digits of n are not present in n^2) of numbers with all different digits. The sequence A059930 (Numbers n such that n and n^2 combined use different digits) is a subsequence of this sequence.
Sequence in context: A243495 A340324 A029783 * A059930 A125965 A111116
KEYWORD
nonn,base,fini,full
AUTHOR
Lekraj Beedassy, Sep 16 2005
EXTENSIONS
More terms from Tanya Khovanova, Dec 25 2006
STATUS
approved