A137100 Numbers k such that k and k^2 use only the digits 2, 4, 6 and 7.

2, 26, 474, 4762

Offset

1,1

Comments

Generated with DrScheme.

No additional terms through 7777777777. - Harvey P. Dale, Dec 08 2015

No additional terms to 10^26. - Robert Israel, Nov 24 2023

Links

Table of n, a(n) for n=1..4.

Jonathan Wellons, Tables of Shared Digits [archived]

Example

4762^2 = 22676644.

Maple

Good:= {2, 4, 6, 7}:
R:= 2:
G[1]:= select(t -> member(t^2 mod 10, Good), Good):
for d from 2 to 26 do
  G[d]:= select(t -> member(floor((t^2 mod 10^d)/10^(d-1)), Good), map(t -> seq(10^(d-1)*i+t, i=Good), G[d-1]));
  for t in G[d] do
    if convert(convert(t^2, base, 10), set) subset Good then  R:= R, t fi
od
od:
R; # Robert Israel, Nov 24 2023

Mathematica

With[{c={2, 4, 6, 7}}, Select[Flatten[Table[FromDigits/@Tuples[c, n], {n, 5}]], SubsetQ[c, IntegerDigits[#^2]]&]] (* Harvey P. Dale, Dec 08 2015 *)

Crossrefs

Sequence in context: A245999 A355725 A285026 * A228411 A364827 A371700

Adjacent sequences: A137097 A137098 A137099 * A137101 A137102 A137103

Keyword

base,nonn,more

Author

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

Status

approved