A136958 Numbers k such that k and k^2 use only the digits 0, 4, 7 and 8.

0, 88, 878, 880, 8780, 8800, 87800, 88000, 878000, 880000, 8780000, 8800000, 87800000, 88000000, 878000000, 880000000, 8780000000, 8800000000, 87800000000, 88000000000, 878000000000, 880000000000, 8780000000000, 8800000000000, 87800000000000, 88000000000000, 878000000000000, 880000000000000

Offset

1,2

Comments

Generated with DrScheme.

Conjectures: (1) the digit 4 never appears in the terms of the sequence (although it does appear in the digits of the squares of the terms of the sequence), and (2) all nonzero terms are of the form 88 * 10^m or 878 * 10^m. - Harvey P. Dale, Oct 24 2020

Links

Table of n, a(n) for n=1..28.

J. Wellons, Tables of Shared Digits [archived]

Example

878^2 = 770884.

Mathematica

With[{c={0, 4, 7, 8}}, Select[FromDigits/@Tuples[c, 15], SubsetQ[ c, IntegerDigits[ #^2]]&]] (* Harvey P. Dale, Oct 24 2020 *)

Crossrefs

Sequence in context: A072432 A136951 A136933 * A137049 A157730 A055749

Adjacent sequences: A136955 A136956 A136957 * A136959 A136960 A136961

Keyword

base,nonn,changed

Author

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

Status

approved