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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 Table of n, a(n) for n=1..4. 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 Adjacent sequences: A137016 A137017 A137018 * A137020 A137021 A137022 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.)