A

self-referential sentence is a sentence that

describes itself in some manner. Classic
examples; "This sentence is true" - or the
derivation of
Epiminides'

paradox, "

This sentence is false".

Another amusing example:

This sentence has three a's, two c's, two d's, nineteen e's, six f's, two g's, five h's, ten i's, two l's, twelve n's, nine o's, five r's, twenty six s's, sixteen t's, four u's,
four v's, eight w's, four x's, and two y's.

Douglas Hofstadter presented some self-referential
sentences in his book

Metamagical Themas, but with
an

emphasis on numbers and how to "construct" them,
such as this one;

In this sentence, the number of occurences of 0 is 1,
of 1 is 11, of 2 is 2, of 3 is 1, of 4 is 1, of 5 is 1,
of 6 is 1, of 7 is 1, of 8 is 1, and of 9 is 1.