A136960 Numbers k such that k and k^2 use only the digits 0, 4, 7 and 9.

0, 7, 70, 97, 700, 970, 997, 7000, 9700, 9970, 9997, 70000, 97000, 99700, 99970, 99997, 700000, 970000, 997000, 999700, 999970, 999997, 7000000, 9700000, 9970000, 9997000, 9999700, 9999970, 9999997, 70000000, 97000000, 99700000, 99970000, 99997000, 99999700, 99999970, 99999997, 700000000, 970000000, 997000000, 999700000, 999970000

Offset

1,2

Comments

Generated with DrScheme.

From Robert Israel, Jun 12 2019: (Start)

If k is in the sequence, then so is 10*k.

Includes 10^a - 3*10^b for b < a.

The rightmost nonzero digit of k must be 7; the leftmost digit must be 0, 7 or 9. (End)

Links

Jonathan Wellons, Table of n, a(n) for n = 1..121

J. Wellons, Tables of Shared Digits [archived]

Example

999999999999997^2 = 999999999999994000000000000009.

Crossrefs

Sequence in context: A061476 A136959 A136952 * A003363 A069542 A063416

Adjacent sequences: A136957 A136958 A136959 * A136961 A136962 A136963

Keyword

base,nonn,changed

Author

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

Status

approved