

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,more,changed


AUTHOR

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


STATUS

approved



