Humans tend to find multiples of $10$ or $5$ more significant when celebrating anniversaries or milestones than other multiples or values. A value of $1000000$ is more significant than a value of $991695$, despite having roughly the same order, and feels more like an "achievement".
Are there other numbers or sequences that could be used in this manner? Like most people use multiples of $10$ or its powers, programmers use multiples of $16$, and hobbits use repdigits, is there any other sequence that is used semi-seriously in the same context?
Such a sequence should be scalable to any order and should have just the right density to feel unique but achievable. For example, prime numbers, while being perfect for finding random things to celebrate, are too dense. Do you have such a favourite sequence? Is there any that is not tied to a specific base ($10, 12, 16$ etc.)?