# Another meaning of the word leptoceratops

I dreamed that a number of the form (10ⁿ−1)/9 was called a "leptoceratops." And it had to be tied up with a squid.

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1. Matt says:

Silly Raymond. It's real name is A002275 (http://oeis.org/A002275)

2. Matt says:

Interesting fact 1: For all X, if X is the Nth leptaceratops and n >= 2, X is the base 2 representation of a Mersenne number (i.e. 2^n-1).

Interesting fact 2: for N >= 2, the Nth leptaceratops is not a perfect square.

3. FriendlyFires says:

And when the squid takes this number without permission, it is called a "kleptoceratops".

4. Falcon says:

For n>=4, it goes up to eleven multiple times!

5. Chris B says:

I'm certainly no mathematician, but I think it can also be described as a sequence (for positive n at least):

f(0) = 1

f(n+1) = f(n) * 10 + 1

6. parkrrrr says:

@Chris B:

Close, but not quite. f(0) is 0.

7. cheong00 says:

I need explanation.

Why squid? Will octopus do?

8. Chris B says:

Doh! Yep. Should have been f(1) = 1, not f(0) = 1.

9. Tony says:

These numbers are actually called repunits.

10. mh says:

That's all well and good, but what's one to do when a Leptosaurus Rex comes along?