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A137019 Numbers k such that k and k^2 use only the digits 1, 2, 7 and 9. 0
1, 11, 27, 2777 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Generated with DrScheme.
No further terms up to 9999999999. - Harvey P. Dale, Oct 13 2020
a(5) > 10^15 if it exists. - Chai Wah Wu, May 25 2021
LINKS
Jonathan Wellons, Tables of Shared Digits [archived]
EXAMPLE
2777^2 = 7711729, so 2777 is a term.
MATHEMATICA
With[{c={1, 2, 7, 9}}, Select[FromDigits/@Flatten[Table[Tuples[c, n], {n, 4}], 1], SubsetQ[ c, IntegerDigits[#^2]]&]] (* Harvey P. Dale, Oct 13 2020 *)
PROG
(Python)
from itertools import product
A137019_list = [n for n in (int(''.join(d)) for l in range(1, 9) for d in product('1279', repeat=l)) if set(str(n**2)) <= set('1279')] # Chai Wah Wu, May 25 2021
CROSSREFS
Sequence in context: A044453 A212776 A362528 * A122929 A030756 A065006
KEYWORD
base,nonn,more,changed
AUTHOR
Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008
STATUS
approved

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Last modified May 20 01:45 EDT 2024. Contains 372703 sequences. (Running on oeis4.)