|
|
A137019
|
|
Numbers k such that k and k^2 use only the digits 1, 2, 7 and 9.
|
|
0
|
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
Generated with DrScheme.
|
|
LINKS
|
|
|
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
|
|
|
KEYWORD
|
base,nonn,changed
|
|
AUTHOR
|
Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008
|
|
STATUS
|
approved
|
|
|
|