A137144 Numbers k such that k and the square of k use only the digits 4, 6, 7 and 8.

8, 88, 8874, 68474, 86478

Offset

1,1

Comments

Generated with DrScheme.

No further terms up to and including 1000000. - Harvey P. Dale, Dec 03 2010

No further terms <= 10^40. - Michael S. Branicky, Feb 12 2024

From Pontus von Brömssen, May 01 2024: (Start)

a(6) > 6*10^46 (if it exists).

If k = x*10^m is a term where 1 < x < 10 and k is not 88 or 8874, then 20/3 < x < 8.7674847468864688448864887688468686674647846475.

(End)

Links

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

Jonathan Wellons, Tables of Shared Digits

Example

86478^2 = 7478444484.

Mathematica

clearQ[n_]:=Module[{dc=DigitCount[n]}, dc[[1]]==dc[[2]]==dc[[3]]==dc[[5]]==dc[[9]]==dc[[10]]==0]
Select[Range[1000000], clearQ[#]&&clearQ[#^2]&] (* Harvey P. Dale, Dec 03 2010 *)

Crossrefs

Cf. A077439, A136809, A136813, A136985, A137028, A137105, A137147.

Sequence in context: A271268 A006750 A082783 * A107677 A084005 A137494

Adjacent sequences: A137141 A137142 A137143 * A137145 A137146 A137147

Keyword

base,nonn,more

Author

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

Status

approved