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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.

J. Wellons, Tables of Shared Digits

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: A044072 A044453 A212776 * A122929 A030756 A065006

Adjacent sequences:  A137016 A137017 A137018 * A137020 A137021 A137022

KEYWORD

base,nonn

AUTHOR

Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008

STATUS

approved

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Last modified October 22 13:15 EDT 2021. Contains 348170 sequences. (Running on oeis4.)