Definition:Untouchable Number/Sequence

Sequence of Untouchable Numbers

The sequence of untouchable numbers begins:

$2, 5, 52, 88, 96, 120, 124, 146, 162, 188, 206, 210, 216, 238, 246, 248, 262, \ldots$

This sequence is A005114 in the On-Line Encyclopedia of Integer Sequences (N. J. A. Sloane (Ed.), 2008).

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $52$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $52$

• Weisstein, Eric W. "Untouchable Number." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/UntouchableNumber.html