A137007 Numbers k such that k and k^2 use only the digits 1, 2, 5 and 7.

1, 5, 11, 15, 715

Offset

1,2

Comments

Generated with DrScheme.

No additional terms up to and including 7,777,777,777. - Harvey P. Dale, Sep 04 2018

No additional terms up to 10^26. - L. Joris Perrenet, Jul 02 2020

No additional terms up to 10^39. - Michael S. Branicky, Apr 12 2024

Links

Table of n, a(n) for n=1..5.

J. Wellons, Tables of Shared Digits [archived]

Example

715^2 = 511225.

Mathematica

Module[{nn=10, c={1, 2, 5, 7}}, Select[Flatten[Table[FromDigits/@Tuples[c, n], {n, nn}]], SubsetQ[c, IntegerDigits[#^2]]&]] (* Harvey P. Dale, Sep 04 2018 *)

Crossrefs

Sequence in context: A221743 A137008 A137010 * A137012 A259067 A314080

Adjacent sequences: A137004 A137005 A137006 * A137008 A137009 A137010

Keyword

base,nonn,changed

Author

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

Status

approved