Computed with engine art-1.0.0. Data updated: 2026-09-26 (UTC). Rules independently implemented by RNGDLE.ART.
Sequences
Rule, exact count and rarity
This pattern alternates between two different decimal digits throughout a number of at least four places. Once the first two positions are chosen, every later digit is fixed by its position parity. The first and second digits must differ, so full repdigits are excluded. The implementation permits both even and odd lengths: a five-digit string such as 12121 alternates correctly even though it ends with an incomplete two-digit block. Zero may occupy one alternating position as long as the written number has no leading zero. Alternation is more restrictive than merely using two distinct digits, so every match also satisfies that alphabet rule. The related sequence signals are weighted within their family rather than counted as independent random events.
The exact count, 243, comes from evaluating all 1,000,001 integers from 0 through 1,000,000, including both endpoints. It is not a sample or an estimate. Each matching integer is counted once for this category, even if it contains multiple qualifying segments. Its frequency of 0.0243% describes the chance that a uniformly chosen integer passes this one test. It is not the global score percentile of every member, and overlapping pattern counts must not be added as if they represented disjoint sets.
The pattern supplies −log₂(243 / 1,000,001) bits before its within-family weight is applied. Other matched patterns, digit sum, distinct-digit count and short-length signals can change the complete score. Consequently, members of this category need not share a ranking. The highest-scoring representative is 5,050, with a rarity score of 1,017 and Top 0.0034%. This uses its complete score across all features, not just this pattern. Equal scores are displayed in ascending numerical order.
Example numbers
ExploreThe highest-scoring match
The highest-scoring representative is 5,050, with a rarity score of 1,017 and Top 0.0034%. This uses its complete score across all features, not just this pattern. Equal scores are displayed in ascending numerical order.
Frequently asked questions
How many alternating two-digit patterns are there between 0 and 1,000,000?
There are exactly 243 matches for alternating two-digit patterns among the 1,000,001 integers from 0 to 1,000,000, inclusive: 0.0243% of the range. At least four places alternate between two distinct digits.
Can an ABAB pattern have an odd number of digits?
Yes. This engine accepts at least four alternating positions, including 12121. It does not require a whole number of two-digit blocks.
What is the highest-scoring alternating two-digit patterns representative?
The highest-scoring representative is 5,050, with a rarity score of 1,017 and Top 0.0034%. This uses its complete score across all features, not just this pattern. Equal scores are displayed in ascending numerical order.