A137064 Numbers k such that k and k^2 use only the digits 1, 6, 7 and 8.

1, 881, 88776, 7866881

Offset

1,2

Comments

Generated with DrScheme.

No additional terms through 10^10. - Harvey P. Dale, Apr 26 2015

No additional terms through 10^27. - Robert Israel, Nov 23 2023

Links

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

Jonathan Wellons, Tables of Shared Digits [archived]

Example

7866881^2 = 61887816668161.

Maple

Good:= {1, 6, 7, 8}:
G[1]:= {1, 6}: R:= 1;
for d from 2 to 27 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:
sort([R]); # Robert Israel, Nov 23 2023

Mathematica

With[{c={1, 6, 7, 8}}, Select[Flatten[Table[FromDigits/@Tuples[c, n], {n, 7}]], SubsetQ[c, IntegerDigits[#^2]]&]] (* Harvey P. Dale, Apr 26 2015 *)

Crossrefs

Sequence in context: A105976 A340342 A265181 * A092675 A135127 A338538

Adjacent sequences: A137061 A137062 A137063 * A137065 A137066 A137067

Keyword

base,nonn,more,changed

Author

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

Status

approved